Snowpack

Snowpack

  • Snowpack forms from layers of snow that accumulate in geographic regions and high elevations where the climate includes cold weather for long periods of the year.

    Snow accumulations are an essential water resource that feeds streams and rivers when they melt. As a result, the snowpack is both the source of drinking water for many communities and a potential source of flooding.

    Snow accumulations also contribute to the mass of glaciers in their area of ​​accumulation.

  • Assessing the formation and stability of snowpacks is vital in studying and forecasting avalanches.

    Scientists study the physical properties of snow under different conditions and their evolution, focusing on snow metamorphism, snow hydrology, the growth of snow cover with climate change, and its effect on ice feedback -albedo and hydrology, both on the ground and using remote sensing.

    Snow is also studied in a more global context of impact on animal habitats and plant succession. Significant effort is devoted to the classification of snow, both as a hydrometeor and on the ground.

Climate Change Indicators: Snowpack

This indicator measures trends in the amount and timing of snow cover in the western United States.

Figure 1. Trends in April Snowpack in the Western United States, 1955–2022

Trends in April Snowpack in the Western United States, 1955–2022
Trends in April Snowpack in the Western United States, 1955–2022


Figure 1. Trends in April Snowpack in the Western United States, 1955-2022

Data source: USDA Natural Resources Conservation Service, 2022
Web update: July 2022
Units: degrees; degrees; percent change

This map shows trends in April snowpack in the western United States, measured as snow water equivalent. Blue circles represent increased snow cover; red circles represent a decrease.

Figure 2. Change in Peak Snowpack Timing in the Western United States, 1982–2021

Change in Peak Snowpack Timing in the Western United States, 1982–2021
Change in Peak Snowpack Timing in the Western United States, 1982–2021


This map shows trends during the year snowpack reaches its maximum in the western United States. Blue triangles represent a shift to later timing; red triangles represent a shift to earlier timing.

State Latitude Longitude Timing total change (days)
AZ 33.65352 -109.309 -26.9671
AZ 33.92123 -109.459 -12.5049
CA 38.608 -119.924 -2.85
CA 41.58233 -120.303 -20.5976
CA 41.99127 -120.18 -1.08293
CA 38.5497 -119.805 -7.32439
CA 38.849 -120.08 -1.13049
CA 38.93403 -120.055 12.5122
CA 38.8519 -119.937 -22.2951
CA 38.92431 -119.916 -1.21098
CA 39.45269 -120.294 -11.4293
CA 39.49001 -120.282 -17.0707
CA 39.42752 -120.313 -0.87073
CA 38.30367 -119.551 -2.86098
CA 38.43745 -119.366 -8.72195
CA 38.50576 -119.626 8.904878
CA 38.99927 -120.131 -7.56951
CA 38.31021 -119.6 -0.34024
CA 39.18986 -120.266 -1.40122
CA 39.17162 -120.154 -19.7854
CA 39.30087 -120.184 0.534146
CA 38.07298 -119.234 -0.33659
CA 39.13545 -120.219 -2.06707
CO 37.33067 -105.068 -33.0988
CO 40.31176 -105.647 -9.76098
CO 39.80364 -105.778 -6.16829
CO 39.08758 -106.542 -12.4866
CO 39.87504 -107.599 -24.4244
CO 38.89435 -106.953 -13.7744
CO 37.65083 -107.806 -8.35976
CO 40.39591 -106.604 -19.5329
CO 39.48917 -106.172 -10.3098
CO 37.20939 -105.2 -5.50976
CO 37.01877 -106.453 -11.3598
CO 40.80572 -105.77 -0.95488
CO 40.5337 -106.781 -14.6012
CO 40.84758 -106.969 -16.2768
CO 39.38014 -106.198 -6.21951
CO 39.64646 -105.869 -7.30244
CO 39.36092 -106.06 0.636585
CO 37.93389 -107.676 -7.77073
CO 39.07543 -106.612 -10.9244
CO 40.53285 -105.887 -6.88537
CO 39.3172 -106.615 -13.3573
CO 39.93659 -105.59 -12.6585
CO 40.41446 -105.819 -13.4963
CO 37.38028 -106.548 -39.5707
CO 37.79895 -107.925 -28.35
CO 37.89169 -108.196 -3.87073
CO 39.12899 -107.288 -23.8207
CO 37.61779 -107.039 -20.389
CO 37.84737 -107.727 -15.8854
CO 40.03581 -105.545 3.72439
CO 38.81982 -106.59 5.341463
CO 39.04433 -107.88 -6.65488
CO 40.39803 -105.846 -12.4098
CO 38.48864 -106.34 -11.8134
CO 37.89168 -107.714 -5.34146
CO 40.87498 -106.047 -6.37683
CO 37.99076 -107.204 -14.5024
CO 40.5374 -106.677 -3.69146
CO 40.03307 -105.576 6.307317
CO 37.48563 -106.835 -19.3683
CO 39.61765 -106.38 -30.5268
CO 37.21423 -105.123 -18.6037
CO 40.34734 -106.095 -7.08659
CO 40.43397 -105.736 1.243902
ID 44.30342 -115.234 -6.92561
ID 44.60533 -116.981 -4.82561
ID 44.62621 -115.796 -7.92439
ID 42.16442 -114.193 -12.1098
ID 44.28846 -115.655 -1.76341
ID 44.437 -111.994 -17.8024
ID 43.6025 -114.674 -20.9415
ID 42.0505 -111.601 -10.4159
ID 43.6104 -113.931 -8.55
ID 43.9538 -115.274 -13.7195
ID 42.32029 -113.616 -8.21341
ID 43.71077 -114.159 -0.2122
ID 42.18072 -114.287 -4.00976
ID 44.4147 -113.398 -17.0488
ID 44.84237 -114.269 -21.3293
ID 45.69694 -115.23 -10.0061
ID 45.18848 -115.972 -8.48049
ID 42.56248 -111.298 -6.8122
ID 42.95275 -111.359 -6.73537
ID 42.76478 -116.9 -14.3159
ID 43.86117 -114.209 -6.89268
ID 43.626 -113.969 -4.89878
ID 43.62903 -115.438 -9.30732
MT 48.5712 -115.446 1.723171
MT 46.09713 -113.13 -0.39512
MT 45.79737 -112.52 -15.2159
MT 44.47147 -112.982 -6.70976
MT 44.94966 -111.359 -4.02805
MT 44.50832 -111.128 4.507317
MT 46.414 -113.431 -8.75854
MT 45.16507 -113.501 -3.45366
MT 46.5596 -111.29 -1.92073
MT 45.2719 -110.249 -11.2756
MT 45.8838 -113.326 -13.4268
MT 44.96192 -111.294 -13.2951
MT 45.01788 -111.846 -2.10732
MT 45.19405 -109.345 5.941463
MT 46.46523 -113.394 -9.02927
MT 47.05678 -112.595 -26.5939
MT 47.08158 -112.73 0.764634
MT 46.78942 -109.512 11.95244
MT 46.18367 -113.853 -9.79024
MT 45.17367 -113.584 -0.63659
MT 46.79279 -110.675 -4.93171
MT 44.79317 -112.056 -5.98902
MT 48.43412 -113.937 -7.62073
MT 45.06235 -109.945 5.359756
MT 48.80225 -113.857 7.412195
MT 46.43545 -112.193 -12.739
MT 48.91453 -114.767 9.834146
MT 48.30754 -114.841 -19.1195
MT 48.9723 -115.953 -10.7378
MT 46.9751 -115.035 6.958537
MT 47.42749 -113.775 3.358537
MT 44.58907 -111.825 -15.8305
MT 44.9938 -113.444 -7.44878
MT 45.5041 -110.966 14.07073
MT 45.50871 -111.923 -2.74024
MT 46.88293 -113.322 -2.22805
MT 44.58623 -111.116 5.85
MT 48.79698 -113.671 2.436585
MT 45.21759 -110.237 -11.8024
MT 47.91727 -112.824 -3.77195
MT 45.40957 -112.959 -2.34878
MT 46.8716 -113.277 4.639024
MT 45.73107 -114.481 -7.17805
MT 48.15678 -113.946 -2.29756
MT 45.00565 -110.014 -11.3159
MT 46.57978 -111.268 6.592683
MT 48.30305 -113.329 -33.6622
MT 45.41905 -110.088 -5.11463
MT 46.11192 -110.47 -8.08171
MT 46.35613 -112.262 -8.87927
MT 46.0896 -110.434 1.141463
MT 45.69259 -113.968 2.7
MT 45.40125 -110.958 0.047561
MT 46.24212 -113.773 -17.7768
MT 46.77962 -110.622 -3.59634
MT 48.90902 -114.863 -6.84512
MT 44.78562 -111.71 -10.4049
MT 46.14287 -114.448 -3.37683
MT 46.1438 -114.506 -8.98537
MT 47.91998 -112.791 7.990244
MT 46.27368 -113.164 -1.6939
MT 44.61088 -111.15 -8.41098
MT 45.04575 -109.91 -3.46829
MT 47.44847 -112.814 -11.261
MT 48.97523 -115.819 11.10366
MT 44.65866 -111.092 -5.19878
MT 46.12588 -113.308 -8.70732
NM 36.51174 -106.315 -21.2341
NM 36.95606 -106.657 -20.9159
NM 36.19418 -105.557 -25.9134
NM 36.71632 -106.264 -9.73902
NM 36.99396 -105.26 -28.4817
NM 35.92195 -106.392 -29.6159
NM 36.69935 -105.341 -22.4195
NM 36.00152 -106.834 -20.3415
NM 33.3696 -108.707 -13.672
NV 41.83384 -115.453 -9.62195
NV 39.31917 -114.623 -4.36098
NV 41.76168 -115.693 -11.2829
NV 39.29148 -117.115 -3.8122
NV 41.75067 -117.532 -4.68293
NV 40.27551 -115.54 -15.9183
NV 40.89343 -115.211 -7.83293
NV 41.82098 -116.102 -13.3463
NV 41.67032 -117.567 -10.8695
NV 40.3848 -115.528 -7.17439
NV 41.54675 -116.005 -11.4329
NV 40.6448 -115.381 -8.38902
NV 41.77637 -116.03 -7.1561
NV 39.16395 -119.897 -5.20976
NV 39.31573 -119.895 -6.03659
NV 41.87255 -115.247 -2.28293
NV 41.73732 -115.472 -4.47805
NV 39.13242 -114.956 -7.69756
OR 45.19085 -119.254 -2.67439
OR 45.14532 -118.219 14.09268
OR 42.05257 -122.855 4.796341
OR 42.40717 -122.266 -3.81585
OR 45.4287 -121.856 -1.44878
OR 44.24767 -118.517 -11.9488
OR 44.83052 -118.188 -23.5646
OR 45.36428 -118.467 -11.3232
OR 43.59042 -122.06 -5.51341
OR 43.22625 -121.807 -4.06098
OR 42.53305 -122.177 -7.29512
OR 44.4465 -119.93 -14.5573
OR 44.86887 -118.114 -17.1695
OR 42.70992 -118.632 -10.3939
OR 42.3801 -122.349 17.6561
OR 42.43933 -122.229 -12.4537
OR 44.7638 -118.312 0.845122
OR 45.69682 -118.107 15.03293
OR 44.42042 -121.857 -30.7793
OR 43.66917 -122.569 -6.29268
OR 43.80368 -121.948 -9.43171
OR 44.21007 -118.638 -22.9207
OR 44.2103 -121.873 -14.7915
OR 45.27173 -117.687 6.245122
OR 45.32097 -121.716 -6.20854
OR 45.26522 -117.174 -6.29268
OR 44.42917 -120.331 -21.5305
OR 45.4643 -121.704 12.02195
OR 43.90098 -122.031 -5.53171
OR 43.61193 -122.118 3.420732
OR 42.69825 -122.142 -6.22317
OR 42.95615 -121.181 -8.08537
OR 42.75333 -118.688 -13.7561
OR 43.94885 -119.54 -6.42439
OR 44.26423 -119.022 3.131707
OR 42.6957 -120.802 -16.2073
OR 43.44907 -122.138 -1.13049
OR 45.07707 -117.551 -8.21707
OR 44.14425 -121.641 -23.2756
OR 44.65567 -118.426 -3.47195
OR 45.06703 -118.152 -8.91951
UT 39.13683 -111.558 -18.3146
UT 40.61233 -111.098 5.330488
UT 41.37603 -111.944 -18.0402
UT 41.38291 -111.921 -22.8329
UT 38.30183 -112.357 2.579268
UT 38.6799 -111.598 -12.4317
UT 38.50809 -112.019 -22.2
UT 40.58102 -110.586 -9.6439
UT 39.134 -111.437 -16.6793
UT 41.68541 -111.42 -8.82073
UT 37.66098 -112.741 -7.02805
UT 40.85464 -111.048 -12.8671
UT 40.88529 -111.07 -0.54512
UT 40.77458 -110.011 -17.6195
UT 39.86671 -111.284 -17.7915
UT 39.89275 -111.252 -6.64024
UT 40.35747 -111.09 -21.1171
UT 40.2953 -111.257 -8.45488
UT 39.04554 -111.469 -10.1159
UT 41.41289 -111.538 -10.8183
UT 40.97462 -111.81 -7.97195
UT 38.77246 -111.677 -8.66707
UT 40.71785 -110.467 -13.6463
UT 38.80034 -111.683 -19.972
UT 37.48997 -112.576 -4.34268
UT 40.79669 -110.885 -17.2427
UT 41.31372 -111.446 -9.91829
UT 39.89166 -110.746 -18.4829
UT 38.48383 -112.393 -19.9939
UT 40.71632 -109.544 -15.2268
UT 37.52664 -113.054 -14.978
UT 40.59709 -110.433 -10.789
UT 38.48226 -109.272 -16.5439
UT 40.86493 -110.798 -18.2854
UT 41.40562 -111.826 -15.2085
UT 37.51255 -113.397 -10.778
UT 39.68338 -111.318 -21.8159
UT 38.30285 -112.436 -4.08293
UT 37.56933 -112.838 -5.63415
UT 41.46547 -111.497 -12.8963
UT 40.60798 -109.888 -18.5159
UT 40.76184 -111.629 2.209756
UT 39.92976 -111.631 -19.9573
UT 39.01219 -111.583 -21.4866
UT 39.45197 -111.272 -13.65
UT 40.54875 -110.693 -0.69146
UT 40.44293 -112.224 -9.02195
UT 39.31042 -111.433 -19.4488
UT 40.78931 -111.092 -2.06707
UT 40.90862 -110.505 -7.6061
UT 40.16483 -111.207 -4.92805
UT 40.42817 -111.616 -8.38902
UT 41.89833 -111.63 -12.0146
UT 40.678 -110.949 3.237805
UT 40.739 -109.673 -12.278
UT 39.93667 -112.415 -10.9317
UT 37.575 -112.902 -8.13293
UT 37.83633 -111.882 -13.9683
WA 47.35037 -120.68 -30.2817
WA 46.27143 -121.963 -6.73902
WA 48.44488 -120.916 0.940244
WA 46.62153 -121.386 -0.70244
WA 47.9909 -120.566 0.493902
WA 47.74607 -121.093 1.309756
WA 46.09497 -121.763 -5.77683
WA 47.23328 -120.294 18.48659
WA 47.28734 -120.37 -5.8061
WA 46.64142 -121.382 2.930488
WY 44.8007 -107.844 -0.17561
WY 43.88743 -107.061 -3.02927
WY 44.94307 -109.567 5.831707
WY 44.37667 -109.793 -0.90732
WY 44.67888 -107.581 3.731707
WY 44.71961 -110.511 9.534146
WY 44.40343 -107.061 -0.99146
WY 41.30399 -107.153 -6.98415
WY 44.57462 -107.295 0.153659
WY 43.00657 -109.759 -3.80488
WY 44.12612 -110.834 -1.52195
WY 43.38939 -110.129 -10.8402
WY 44.25602 -106.98 1.821951
WY 42.86984 -109.095 3.585366
WY 43.86067 -109.322 -3.62561
WY 44.20862 -110.666 -0.36951
WY 43.50278 -109.752 -7.18902
WY 43.17387 -110.14 -7.1378
WY 43.62728 -107.181 -11.2646
WY 41.33087 -106.376 -8.65244
WY 41.15397 -106.969 4.218293
WY 43.65868 -109.01 -6.30732
WY 44.73396 -109.915 -8.84634
WY 43.51687 -110.913 -14.4366
WY 44.16188 -107.126 -6.16829
WY 42.5075 -110.91 -2.21341
WY 44.50012 -107.429 -0.6878
WY 41.3295 -106.503 -15.0915
WY 44.7225 -107.4 0.12439
WY 44.47764 -110.157 -20.6451
WY 43.74902 -110.058 -8.43293
WY 42.69525 -108.896 -0.95488
WY 44.15178 -110.221 -6.69878
WY 41.1591 -106.928 -12.4537
WY 44.80417 -109.657 -9.69878

Figure 2. Change in Peak Snowpack Timing in the Western United States, 1982-2021
Data source: USDA Natural Resources Conservation Service, 2022
Web update: July 2022
Units: degrees; degrees; days

Figure 3. Average Date of Peak Snowpack in the Western United States, 1982–2021

Average Date of Peak Snowpack in the Western United States, 1982–2021 This graph shows trends during the year snowpack reaches its maximum in the western United States. The line in this graph represents the average of all the locations shown in Figure 2.  Water year	Peak date 1982	198.8963 1983	209.4482 1984	204.3232 1985	187.8689 1986	185.9451 1987	186.5854 1988	187.2378 1989	183.2409 1990	185.8079 1991	199.5732 1992	176.9451 1993	194.0793 1994	185.9299 1995	199.6829 1996	192.6402 1997	189.9451 1998	195.0427 1999	199.5579 2000	184.0366 2001	191.0244 2002	186.1433 2003	194.2652 2004	174.75 2005	193.6433 2006	191.7896 2007	177.6524 2008	197.5091 2009	196.375 2010	199 2011	206.5305 2012	181.7073 2013	186.6311 2014	187.5427 2015	164.1616 2016	182.061 2017	184.1433 2018	188.4512 2019	191.5915 2020	190.314 2021	185.7073 Figure 3. Average Date of Peak Snowpack in the Western United States, 1982-2021 Data source: USDA Natural Resources Conservation Service, 2022 Web update: July 2022 Units: day of water year  Figure 4. Change in Snowpack Season Length in the Western United States, 1982–2021 Change in Snowpack Season Length in the Western United States, 1982–2021 Change in Snowpack Season Length in the Western United States, 1982–2021 This map shows trends in the length of the western United States snowpack season in days. Blue circles show where the season has extended; red circles indicate where it has shortened.  State	Latitude	Longitude	Duration total change (days) CO	37.33	-105.07	-25.372 OR	45.19	-119.25	-21.1427 AZ	34.46	-111.41	-37.9793 WY	44.8	-107.84	-7.85122 AZ	33.98	-109.5	-74.3927 MT	48.57	-115.45	-16.1854 ID	44.3	-115.23	-20.25 MT	46.1	-113.13	6.329268 MT	45.8	-112.52	-19.0024 NM	36.51	-106.32	-32.6963 MT	44.47	-112.98	8.147561 NV	41.83	-115.45	-21.9037 CO	40.31	-105.65	-2.95976 WY	43.89	-107.06	4.917073 WY	44.94	-109.57	12.16463 MT	44.95	-111.36	-9.5378 UT	39.14	-111.56	-35.0963 UT	40.61	-111.1	-2.56829 OR	45.15	-118.22	-7.27895 UT	41.38	-111.94	-33.0951 UT	41.38	-111.92	-26.2134 NV	39.32	-114.62	-19.4085 CO	39.8	-105.78	-3.91098 NV	41.76	-115.69	1.62439 NV	39.29	-117.12	-17.1915 ID	44.63	-115.8	-21.3512 UT	38.3	-112.36	-33.0526 OR	42.05	-122.85	-12.1098 OR	42.41	-122.27	-28.4598 MT	44.51	-111.13	4.093902 UT	38.68	-111.6	-22.3756 MT	46.41	-113.43	-18.3329 WY	44.38	-109.79	3.373171 OR	45.43	-121.86	-32.8354 WA	47.35	-120.68	-43.9061 WY	42.96	-110.61	10.13415 MT	45.17	-113.5	-3.61463 CA	38.61	-119.92	-41.3963 OR	44.25	-118.52	-17.46 WY	44.68	-107.58	-4.57683 ID	42.16	-114.19	-8.5061 MT	46.56	-111.29	11.24268 OR	44.83	-118.19	-17.561 OR	45.36	-118.47	-18.128 MT	45.27	-110.25	-11.0634 UT	38.51	-112.02	-32.5683 UT	40.58	-110.59	-28.1049 CO	39.09	-106.54	3.365854 UT	39.13	-111.44	-45.3256 NV	41.75	-117.53	-9.15 UT	41.69	-111.42	-13.9244 CO	39.88	-107.6	-14.8902 CO	38.89	-106.95	-12.7463 MT	45.88	-113.33	-22.8512 WY	44.72	-110.51	-5.20864 MT	44.96	-111.29	-1.17805 CO	37.65	-107.81	-26.9927 OR	43.59	-122.06	-13.8915 UT	37.66	-112.74	-33.161 CA	41.58	-120.3	-26.9341 UT	40.85	-111.05	-29.5244 UT	40.89	-111.07	-2.37439 NM	36.96	-106.66	-8.04878 OR	43.23	-121.81	-41.0927 UT	40.77	-110.01	-15.0366 OR	45.1	-121.75	-12.7939 UT	39.87	-111.28	-28.3793 UT	39.89	-111.25	-24.2524 OR	45.19	-121.69	-37.1488 WY	44.4	-107.06	-2.36341 MT	45.02	-111.85	1.335366 OR	42.53	-122.18	-28.3317 MT	45.19	-109.35	-7.0061 CO	40.4	-106.6	-11.8134 MT	46.47	-113.39	-15.8561 MT	47.06	-112.6	-63.3256 MT	47.08	-112.73	-0.6 CO	39.49	-106.17	4.039024 AZ	33.8	-109.15	-51 NV	40.28	-115.54	-20.2134 WA	47.28	-121.67	-54.9512 OR	45.19	-118.55	-45.3079 ID	44.29	-115.66	-21.5305 ID	44.44	-111.99	-13.8402 MT	46.79	-109.51	14.06341 CO	37.21	-105.2	6.753659 CO	37.02	-106.45	-9.8378 UT	40.36	-111.09	-31.4561 MT	46.18	-113.85	-6.27439 OR	44.52	-122.09	-55.6939 UT	40.3	-111.26	-19.3902 MT	45.17	-113.58	12.71707 MT	46.79	-110.68	0.808537 CO	40.81	-105.77	-4.5878 OR	44.45	-119.93	-19.2 UT	39.05	-111.47	-20.7711 NV	41.97	-118.19	-61.2915 CA	41.99	-120.18	-6.99512 MT	44.79	-112.06	-11.1402 WY	41.3	-107.15	-20.9854 ID	43.6	-114.67	-19.178 WY	44.57	-107.3	-7.50366 NV	40.89	-115.21	-7.4122 UT	41.41	-111.54	-15.3329 CO	40.53	-106.78	4.32439 CA	38.55	-119.8	-40.7561 CA	38.85	-120.08	-22.3866 OR	44.87	-118.11	-26.6817 CO	40.85	-106.97	-4.13684 WY	43.01	-109.76	-3.48293 MT	48.43	-113.94	-16.8805 OR	45.56	-118.45	-31.4415 CA	38.93	-120.05	-20.4037 UT	40.97	-111.81	-13.7744 UT	38.77	-111.68	-17.122 NV	41.82	-116.1	-29.1329 OR	42.71	-118.63	-22.7085 OR	42.38	-122.35	-15.45 MT	45.06	-109.94	3.42439 UT	40.72	-110.47	-18.3549 MT	48.8	-113.86	5.813415 OR	42.44	-122.23	-25.7305 ID	42.05	-111.6	-14.9598 CO	39.38	-106.2	-4.37927 NM	33.74	-108.94	-36.3366 MT	46.44	-112.19	-22.7963 AZ	35.07	-111.84	-8.0378 NM	36.19	-105.56	-35.2974 ID	43.61	-113.93	-9.39512 OR	44.76	-118.31	-1.68659 UT	38.8	-111.68	-19.8255 NV	41.67	-117.57	-30.9037 WY	44.13	-110.83	-10.7524 MT	48.91	-114.77	-2.85366 NV	40.38	-115.53	-16.2402 OR	45.62	-121.7	-28.8439 CO	39.65	-105.87	1.792683 WY	43.39	-110.13	-5.84634 CA	38.85	-119.94	-8.53171 MT	48.31	-114.84	-29.6085 AZ	33.65	-109.31	-50.3012 WY	44.26	-106.98	-2.06341 UT	37.49	-112.58	-34.5832 MT	48.97	-115.95	-14.572 UT	40.8	-110.88	-26.9854 CA	38.92	-119.92	-28.65 OR	45.7	-118.11	8.652439 WY	42.87	-109.09	-4.8 OR	44.42	-121.86	-75.7866 OR	43.67	-122.57	-57.3474 MT	46.98	-115.03	0.164634 CO	39.36	-106.06	3.391463 NM	36.72	-106.26	-19.7012 UT	41.31	-111.45	-12.8085 CO	37.93	-107.68	-7.75976 CA	39.45	-120.29	-43.2366 CA	39.49	-120.28	-39.6329 CA	39.43	-120.31	-14.3341 CO	39.08	-106.61	2.436585 UT	39.89	-110.75	-31.4378 OR	43.8	-121.95	-21.0553 NV	41.55	-116.01	-20.6451 CO	40.53	-105.89	-18.161 OR	44.39	-122.17	-63.5049 CO	39.32	-106.62	-7.67927 UT	38.48	-112.39	-37.5073 OR	42.72	-123.2	-9.00732 UT	40.72	-109.54	-23.7073 WY	43.86	-109.32	-9.79024 UT	37.53	-113.05	-23.539 MT	47.43	-113.78	-25.9098 OR	44.21	-118.64	-20.0605 CO	39.94	-105.59	10.54024 CO	40.41	-105.82	-8.43293 UT	40.6	-110.43	-12.3805 MT	44.59	-111.82	-24.8122 NV	41.52	-117.63	-75.2159 NV	40.64	-115.38	-26.3012 UT	38.48	-109.27	-25.6427 NV	41.78	-116.03	-25.189 CA	38.3	-119.55	-33.4866 MT	44.99	-113.44	-20.6415 WY	44.21	-110.67	-16.7524 MT	45.5	-110.97	-5.3122 UT	40.86	-110.8	-22.628 CO	37.38	-106.55	-16.3024 UT	41.41	-111.83	-17.4732 WY	43.5	-109.75	-0.96585 CO	37.8	-107.92	-21.589 CA	38.44	-119.37	-41.111 CO	37.89	-108.2	-13.9354 WA	46.27	-121.96	-17.2885 UT	37.51	-113.4	-33.6402 NM	33.36	-107.83	-52.3573 WY	43.17	-110.14	-7.98293 MT	45.51	-111.92	4.558537 MT	46.88	-113.32	-18.6073 OR	45.27	-118.85	-31.6902 MT	44.59	-111.12	-7.3939 ID	42.18	-114.29	-7.41585 UT	39.68	-111.32	-25.2293 MT	48.8	-113.67	-10.0354 OR	44.59	-121.97	-49.2695 NV	39.16	-119.9	-14.0598 AZ	33.92	-109.46	-64.1159 CO	39.13	-107.29	-21.0512 OR	44.21	-121.87	-24.7658 UT	38.3	-112.44	-15.7939 CO	37.62	-107.04	-8.99268 WY	43.63	-107.18	-27.4317 UT	37.57	-112.84	-32.9243 CO	37.85	-107.73	-2.32317 UT	41.47	-111.5	-11.3159 MT	45.22	-110.24	-5.22805 AZ	34.94	-111.52	-51.3585 UT	40.61	-109.89	-16.1232 OR	45.27	-117.69	7.664634 MT	47.92	-112.82	-4.14146 ID	45.7	-115.23	-0.99878 OR	45.32	-121.72	-18.2122 NV	39.32	-119.89	-26.5024 OR	45.27	-117.17	12.05122 MT	45.41	-112.96	8.165854 MT	46.87	-113.28	-7.2878 OR	43.51	-121.98	-15.5415 MT	45.73	-114.48	-11.7476 CO	40.04	-105.55	10.93171 MT	48.16	-113.95	-2.5061 NM	36.99	-105.26	-43.4159 OR	45.55	-122	8.937805 WY	41.33	-106.38	-10.3829 MT	45.01	-110.01	-16.7561 OR	44.43	-120.33	-35.5207 WY	41.15	-106.97	-0.49756 WY	43.66	-109.01	-5.44756 CO	38.82	-106.59	14.30854 WA	48.44	-120.92	-20.3598 CO	39.04	-107.88	-11.8976 WY	44.73	-109.91	-14.528 UT	40.76	-111.63	-8.07073 UT	39.93	-111.63	-44.7841 OR	45.04	-121.93	-47.3211 CO	40.4	-105.85	-6.88171 WY	43.52	-110.91	2.392105 MT	46.58	-111.27	-0.57073 UT	39.01	-111.58	-30.622 WA	46.62	-121.39	8.509756 MT	48.3	-113.33	-58.6354 MT	45.42	-110.09	-9.46463 CA	38.51	-119.63	2.129268 NV	41.87	-115.25	-0.93293 WA	47.99	-120.57	-16.5293 MT	46.11	-110.47	-22.639 CO	38.49	-106.34	-5.08902 WY	44.16	-107.13	1.803659 OR	42.32	-120.83	-101.879 NM	35.92	-106.39	-60.4207 OR	43.66	-122.21	-2.79146 OR	45.46	-121.7	-29.8683 CO	37.89	-107.71	-1.44878 UT	39.45	-111.27	-33.5122 NM	36.7	-105.34	-29.5098 CO	40.87	-106.05	5.012195 OR	43.9	-122.03	-27.8085 UT	40.55	-110.69	-7.3061 OR	44.01	-118.84	-17.6524 MT	46.36	-112.26	1.979268 UT	40.44	-112.22	-32.1988 CA	39	-120.13	-27.439 MT	46.09	-110.43	-17.5756 OR	45.54	-123.37	-46.1817 MT	45.69	-113.97	5.670732 OR	43.61	-122.12	-27.7829 WY	42.51	-110.91	-3.62561 OR	44.44	-121.95	-42.8963 UT	39.31	-111.43	-41.2573 OR	45.53	-123.3	-75.611 NM	36	-106.83	-39.45 OR	42.7	-122.14	-12.5195 NV	41.74	-115.47	-28.4671 WY	44.5	-107.43	-3.62561 MT	45.4	-110.96	5.381707 NM	32.92	-108.15	-82.8711 OR	42.96	-121.18	-28.0427 MT	46.24	-113.77	-17.7622 ID	42.56	-111.3	-13.2805 CO	37.99	-107.2	-13.1524 UT	40.79	-111.09	-19.2732 CA	38.31	-119.6	-22.7305 WY	41.33	-106.5	-23.6341 ID	42.76	-116.9	-32.3671 CA	38.67	-119.82	3.62561 MT	46.78	-110.62	2.443902 CA	39.19	-120.27	-38.0707 MT	48.91	-114.86	-0.51585 OR	44.26	-119.02	-14.9634 UT	40.91	-110.5	-16.6756 WA	47.75	-121.09	-10.6317 OR	42.13	-120.84	-48.9111 UT	40.16	-111.21	-20.1695 WY	44.72	-107.4	2.630488 OR	42.7	-120.8	-12.3 OR	43.45	-122.14	-9.88256 WA	46.09	-121.76	-2.98293 ID	43.63	-113.97	-11.9488 WY	44.48	-110.16	-15.7756 CA	39.17	-120.15	-65.4695 OR	42.69	-121.43	-26.3817 NV	41.23	-116.03	-35.0671 OR	45.08	-117.55	-17.9053 MT	44.79	-111.71	-35.9378 OR	44.14	-121.64	-38.0783 UT	40.43	-111.62	-18.8963 OR	44.66	-118.43	-5.59756 WY	43.75	-110.06	-0.22317 UT	41.9	-111.63	-13.8951 CO	40.54	-106.68	-18.9037 WY	42.7	-108.9	2.078049 UT	40.68	-110.95	-11.7476 WA	47.23	-120.29	9.6 UT	40.74	-109.67	-25.9317 CA	39.3	-120.18	-16.5329 MT	46.14	-114.45	-1.8622 MT	46.14	-114.51	-13.7561 WY	44.15	-110.22	-8.96707 CO	40.03	-105.58	4.964634 CO	37.49	-106.84	-18.4939 WA	47.29	-120.37	-2.01585 CO	39.62	-106.38	-41.3232 UT	39.94	-112.41	-31.672 CA	38.07	-119.23	-38.0598 MT	47.92	-112.79	-0.68415 CA	39.14	-120.22	-22.5402 NV	39.13	-114.96	-23.989 MT	46.27	-113.16	10.68659 WY	41.16	-106.93	-2.52073 UT	37.58	-112.9	-32.9268 CO	37.21	-105.12	-2.22805 MT	44.61	-111.15	-7.30244 AZ	35.14	-112.15	-53.4768 MT	45.05	-109.91	5.264634 UT	37.84	-111.88	-16.222 CO	40.35	-106.1	5.385366 CO	40.43	-105.74	2.392683 OR	45.07	-118.15	-18.0237 WY	44.8	-109.66	-11.55 MT	47.45	-112.81	-2.22805 AZ	33.81	-110.92	-42.7579 MT	48.17	-109.65	-25.6902 MT	48.98	-115.82	5.678049 MT	44.66	-111.09	-20.561 MT	46.13	-113.31	-3.69878 Figure 4. Change in Snowpack Season Length in the Western United States, 1982–2021 Data source: USDA Natural Resources Conservation Service, 2022 Web update: July 2022 Units: number of days of snow season duration  Key points From 1955 to 2022, April snow cover decreased at 93 percent of measured locations (see Figure 1). The average change across all sites is about a 23 percent decrease. A significant and consistent decrease in April snowpack was observed across the western United States (see Figure 1). The decline was particularly pronounced in Washington, Oregon, northern California, and the Rockies. While some stations saw an increase in April snowpack, all 12 states included in this indicator saw an average decrease between 1955 and 2022 (see Figure 1). In the Northwest, all but three stations saw a decline in snow cover during the period of record. About 84 percent of sites experienced a shift toward an earlier snowpack peak (see Figure 2). This earlier trend is particularly pronounced in southwestern states such as Colorado, New Mexico, and Utah. At all stations, maximum snow cover has moved earlier by an average of nearly eight days since 1982 (see Figure 3), based on the long-term average rate of change. From 1982 to 2021, the snowpack season shortened in about 86 percent of the locations where snowpack was measured. In all places, the length of the snow season was reduced by about 18 days on average. Background Temperature and precipitation are key factors affecting snowpack, the amount or thickness of snow that accumulates on the ground. In a warming climate, most areas are expected to see more precipitation as rain than snow – reducing the extent and depth of the snowpack. Long-term observations in the contiguous 48 states show that nearly 80 percent of weather stations surveyed saw a decrease in the proportion of precipitation falling as snow. In addition, with warmer winters and springs, the seasonality of the snow cover also changes. Warmer temperatures cause snow to melt earlier, which in turn affects the timing and availability of water. Mountain snowpack plays a crucial role in the water cycle in western North America, storing water in the winter when snow falls and releasing it as runoff in the spring and summer when the snow melts. Millions of people in the West depend on melting mountain snowpacks for hydropower, irrigation, and drinking water. In most western watersheds, the snowpack is a more prominent component of water supplies than man-made reservoirs. In the future, continued snowpack reductions and snowmelt shifts are expected to reduce hydropower generation in the Southwest and Northwest. Changes in mountain snowpack can affect agriculture, winter recreation, and tourism in some areas, as well as plants and wildlife. For example, some species of trees rely on snow for insulation from frost, as do some species of animals. In addition, fish spawning can be disrupted if changes in snow cover or snowmelt alter the timing and amount of flows. In addition, warming and earlier snowmelt are accelerating the start of the fire season and encouraging more wildfire activity in the western United States and Alaska. The sensitivity of snowpack to climate and its many associated effects make it a valuable indicator to monitor. About the indicator This indicator uses a measurement called snow water equivalent to determine snowpack trends. Snow water equivalent is the amount of water in the snow cover at a particular location. It can be thought of as the depth of water that would be created if the entire snowpack melted. Figure 1 shows the long-term rate of change for April 1, the most common observation date, because it could reflect differences in precipitation and is widely used for spring streamflow and water supply forecasts. Figures 2 and 3 focus on the day of each year when the snowpack is deepest to determine whether it occurs earlier or later. Figure 4 shows changes in the length of the snowpack season, which represents the number of days the ground is covered with continuous snowpacks. The USDA and other collaborators have measured snow cover since the early 20th century. In the early years of data collection, researchers measured snow water equivalent by hand. Still, since 1980, measurements have been collected at some locations using automated instruments as part of a snow telemetry network. The long-term analysis in Figure 1 is based on data from nearly 700 permanent measurement sites in the western United States. The snow cover analysis shown in Figures 2, 3, and 4 requires daily measurements, so it uses a smaller set of 328 SNOTEL sites that have data since 1982, when many SNOTEL devices were deployed and online. About the Data Notes on the indicator EPA chose 1955 as the starting point for Figure 1 because many measurement sites in the Southwest were established in the early 1950s. The natural variability of Earth’s climate means snowpack trends can vary slightly when measured over different periods. For example, the period from 1945 to 1955 was unusually snowy in the Northwest, so if this indicator started in 1945 or 1950, the Northwest would appear to show more significant declines over time. However, the general direction of the trend is the same regardless of the start date. The peak snow cover analysis in Figures 2, 3, and 4 is limited to automated SNOTEL stations, resulting in a shorter time and fewer stations than in Figure 1. These analyzes are subject to less interannual variation than a single-date time series such as 1st April. However, snowpack conditions during the first few years (in this case, the early to mid-1980s) could still have a sizable influence on the trends calculated for this indicator. Although most parts of the West experienced a decrease in snowpack—in line with the overall warming trends shown in the U.S. and the Global Temperature Indicator—snowfall trends may be partly influenced by non climatic factors such as observation methods, land use changes, and forest cover. Changes. This indicator applies consistent methods to all locations, but each site naturally has unique local conditions and a unique distribution of data. In many areas where the snowpack is increasing, studies have documented that despite general increases in temperature and precipitation, temperatures often remain below freezing, leading to more snow. Data Sources The data for this indicator comes from the US Department of Agriculture’s Center for Conservation of Natural Resources for Water and Climate. This indicator’s April 1 trend analysis was created using methods consistent with Mote et al. and Mote et al. peak snowpack analysis adapted from Evan’s work. Snowpack season length was calculated using Petersky and Harpold’s methods. This entry was posted in USA. Bookmark the permalink.  NHI NHI  Climate Change Indicators: Snow Cover Climate Change Indicators: Permafrost  Leave a Reply  Logged in as nhi nhi. Log out?  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Average Date of Peak Snowpack in the Western United States, 1982–2021

This graph shows trends during the year snowpack reaches its maximum in the western United States. The line in this graph represents the average of all the locations shown in Figure 2.

Water year Peak date
1982 198.8963
1983 209.4482
1984 204.3232
1985 187.8689
1986 185.9451
1987 186.5854
1988 187.2378
1989 183.2409
1990 185.8079
1991 199.5732
1992 176.9451
1993 194.0793
1994 185.9299
1995 199.6829
1996 192.6402
1997 189.9451
1998 195.0427
1999 199.5579
2000 184.0366
2001 191.0244
2002 186.1433
2003 194.2652
2004 174.75
2005 193.6433
2006 191.7896
2007 177.6524
2008 197.5091
2009 196.375
2010 199
2011 206.5305
2012 181.7073
2013 186.6311
2014 187.5427
2015 164.1616
2016 182.061
2017 184.1433
2018 188.4512
2019 191.5915
2020 190.314
2021 185.7073


Figure 3. Average Date of Peak Snowpack in the Western United States, 1982-2021
Data source: USDA Natural Resources Conservation Service, 2022
Web update: July 2022
Units: day of water year

Figure 4. Change in Snowpack Season Length in the Western United States, 1982–2021

Change in Snowpack Season Length in the Western United States, 1982–2021
Change in Snowpack Season Length in the Western United States, 1982–2021


This map shows trends in the length of the western United States snowpack season in days. Blue circles show where the season has extended; red circles indicate where it has shortened.

State Latitude Longitude Duration total change (days)
CO 37.33 -105.07 -25.372
OR 45.19 -119.25 -21.1427
AZ 34.46 -111.41 -37.9793
WY 44.8 -107.84 -7.85122
AZ 33.98 -109.5 -74.3927
MT 48.57 -115.45 -16.1854
ID 44.3 -115.23 -20.25
MT 46.1 -113.13 6.329268
MT 45.8 -112.52 -19.0024
NM 36.51 -106.32 -32.6963
MT 44.47 -112.98 8.147561
NV 41.83 -115.45 -21.9037
CO 40.31 -105.65 -2.95976
WY 43.89 -107.06 4.917073
WY 44.94 -109.57 12.16463
MT 44.95 -111.36 -9.5378
UT 39.14 -111.56 -35.0963
UT 40.61 -111.1 -2.56829
OR 45.15 -118.22 -7.27895
UT 41.38 -111.94 -33.0951
UT 41.38 -111.92 -26.2134
NV 39.32 -114.62 -19.4085
CO 39.8 -105.78 -3.91098
NV 41.76 -115.69 1.62439
NV 39.29 -117.12 -17.1915
ID 44.63 -115.8 -21.3512
UT 38.3 -112.36 -33.0526
OR 42.05 -122.85 -12.1098
OR 42.41 -122.27 -28.4598
MT 44.51 -111.13 4.093902
UT 38.68 -111.6 -22.3756
MT 46.41 -113.43 -18.3329
WY 44.38 -109.79 3.373171
OR 45.43 -121.86 -32.8354
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Figure 4. Change in Snowpack Season Length in the Western United States, 1982–2021
Data source: USDA Natural Resources Conservation Service, 2022
Web update: July 2022
Units: number of days of snow season duration

Key points

  • From 1955 to 2022, April snow cover decreased at 93 percent of measured locations (see Figure 1). The average change across all sites is about a 23 percent decrease.
  • A significant and consistent decrease in April snowpack was observed across the western United States (see Figure 1).

    The decline was particularly pronounced in Washington, Oregon, northern California, and the Rockies.
  • While some stations saw an increase in April snowpack, all 12 states included in this indicator saw an average decrease between 1955 and 2022 (see Figure 1).

    In the Northwest, all but three stations saw a decline in snow cover during the period of record.
  • About 84 percent of sites experienced a shift toward an earlier snowpack peak (see Figure 2). This earlier trend is particularly pronounced in southwestern states such as Colorado, New Mexico, and Utah.

    At all stations, maximum snow cover has moved earlier by an average of nearly eight days since 1982 (see Figure 3), based on the long-term average rate of change.
  • From 1982 to 2021, the snowpack season shortened in about 86 percent of the locations where snowpack was measured. In all places, the length of the snow season was reduced by about 18 days on average.

Background

  • Temperature and precipitation are key factors affecting snowpack, the amount or thickness of snow that accumulates on the ground.

    In a warming climate, most areas are expected to see more precipitation as rain than snow – reducing the extent and depth of the snowpack.

    Long-term observations in the contiguous 48 states show that nearly 80 percent of weather stations surveyed saw a decrease in the proportion of precipitation falling as snow.

    In addition, with warmer winters and springs, the seasonality of the snow cover also changes. Warmer temperatures cause snow to melt earlier, which in turn affects the timing and availability of water.

  • Mountain snowpack plays a crucial role in the water cycle in western North America, storing water in the winter when snow falls and releasing it as runoff in the spring and summer when the snow melts.

    Millions of people in the West depend on melting mountain snowpacks for hydropower, irrigation, and drinking water. In most western watersheds, the snowpack is a more prominent component of water supplies than man-made reservoirs. In the future, continued snowpack reductions and snowmelt shifts are expected to reduce hydropower generation in the Southwest and Northwest.

  • Changes in mountain snowpack can affect agriculture, winter recreation, and tourism in some areas, as well as plants and wildlife. For example, some species of trees rely on snow for insulation from frost, as do some species of animals.

    In addition, fish spawning can be disrupted if changes in snow cover or snowmelt alter the timing and amount of flows. In addition, warming and earlier snowmelt are accelerating the start of the fire season and encouraging more wildfire activity in the western United States and Alaska.

    The sensitivity of snowpack to climate and its many associated effects make it a valuable indicator to monitor.

About the indicator

  1. This indicator uses a measurement called snow water equivalent to determine snowpack trends. Snow water equivalent is the amount of water in the snow cover at a particular location.

    It can be thought of as the depth of water that would be created if the entire snowpack melted. Figure 1 shows the long-term rate of change for April 1, the most common observation date, because it could reflect differences in precipitation and is widely used for spring streamflow and water supply forecasts.

    Figures 2 and 3 focus on the day of each year when the snowpack is deepest to determine whether it occurs earlier or later.

    Figure 4 shows changes in the length of the snowpack season, which represents the number of days the ground is covered with continuous snowpacks.

  2. The USDA and other collaborators have measured snow cover since the early 20th century. In the early years of data collection, researchers measured snow water equivalent by hand.

    Still, since 1980, measurements have been collected at some locations using automated instruments as part of a snow telemetry network. The long-term analysis in Figure 1 is based on data from nearly 700 permanent measurement sites in the western United States.

    The snow cover analysis shown in Figures 2, 3, and 4 requires daily measurements, so it uses a smaller set of 328 SNOTEL sites that have data since 1982, when many SNOTEL devices were deployed and online.

About the Data

Notes on the indicator

  • EPA chose 1955 as the starting point for Figure 1 because many measurement sites in the Southwest were established in the early 1950s. The natural variability of Earth’s climate means snowpack trends can vary slightly when measured over different periods.

    For example, the period from 1945 to 1955 was unusually snowy in the Northwest, so if this indicator started in 1945 or 1950, the Northwest would appear to show more significant declines over time.

    However, the general direction of the trend is the same regardless of the start date. The peak snow cover analysis in Figures 2, 3, and 4 is limited to automated SNOTEL stations, resulting in a shorter time and fewer stations than in Figure 1.

    These analyzes are subject to less interannual variation than a single-date time series such as 1st April. However, snowpack conditions during the first few years (in this case, the early to mid-1980s) could still have a sizable influence on the trends calculated for this indicator.

  • Although most parts of the West experienced a decrease in snowpack—in line with the overall warming trends shown in the U.S. and the Global Temperature Indicator—snowfall trends may be partly influenced by non climatic factors such as observation methods, land use changes, and forest cover.

    Changes. This indicator applies consistent methods to all locations, but each site naturally has unique local conditions and a unique distribution of data.

    In many areas where the snowpack is increasing, studies have documented that despite general increases in temperature and precipitation, temperatures often remain below freezing, leading to more snow.

Data Sources

The data for this indicator comes from the US Department of Agriculture’s Center for Conservation of Natural Resources for Water and Climate.

This indicator’s April 1 trend analysis was created using methods consistent with Mote et al. and Mote et al. peak snowpack analysis adapted from Evan’s work. Snowpack season length was calculated using Petersky and Harpold’s methods.

Weather 01852 - Lowell MA

moderate rain

49°

moderate rain

Feels like 49°
Sunrise/Sunset - 01852
Sunrise/Sunset

06:33/19:06

Temperature - 01852
High/Low

52°F

/

46°F

Humidity in 01852
Humidity

85%

Pressure
Pressure

1013 hPa

Visibility
Visibility

7 mi

Wind
Wind

1.01 mph