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Frost Date Finder

NOAA 1991–2020 freeze normals

Frost Dates in Wyoming

Last and first frost at the 34 NOAA stations behind this site's Wyoming pages.

At the middle station of the 34 in Wyoming where a freeze comes every year, the last spring frost (50%) is May 21 and the first fall frost September 23, a freeze-free season of 124 days. The last frost is earliest at Worland (Worland, WY, May 4) and latest at Afton (Afton, WY, June 20), 47 days apart. The season runs from 70 days at Jackson to 152 at Thermopolis.

22 of these stations were also in NOAA's previous normals, for 1981–2010. Between the two, the median station's freeze-free season grew 1 day longer and the first fall frost 1 day later; the season lengthened at 11 stations and shortened at 10. The two periods share twenty years, so the change reflects mostly 2011–2020 against 1981–1990.

Wyoming places by frost date

Frost dates of the Wyoming places with a page, largest first
PlaceZIPLast frostFirst frostSeasonWinters with 32°F
Cheyenne82001May 14October 1139 d100%
Cheyenne82009May 12October 1141 d100%
Casper82604May 26September 22117 d100%
Rock Springs82901May 24September 24121 d100%
Casper82601May 10September 29138 d100%
Gillette82718May 25September 23120 d100%
Sheridan82801May 21September 23123 d100%
Laramie82070June 2September 15102 d100%
Riverton82501May 12September 24132 d100%
Casper82609May 12October 1143 d100%
Jackson83001June 20August 3170 d100%
Gillette82716May 22September 25125 d100%
Laramie82072June 7September 488 d100%
Cody82414May 17October 3136 d100%
Evanston82930June 12September 1290 d100%
Lander82520May 13October 2140 d100%
Powell82435May 19September 20123 d100%
Green River82935May 24September 22120 d100%
Torrington82240May 14September 24130 d100%
Douglas82633May 23September 22122 d100%
Rawlins82301May 17October 2138 d100%
Buffalo82834May 24September 21118 d100%
Worland82401May 4October 1149 d100%
Wheatland82201May 19September 22125 d100%
Newcastle82701May 13October 3143 d100%
Afton83110June 20September 171 d100%
Thermopolis82443May 5October 5152 d100%
Lyman82937June 14September 984 d100%
Lovell82431May 9September 29142 d100%
Greybull82426May 11September 23133 d100%
Moorcroft82721May 23September 20118 d100%
Big Piney83113June 9September 484 d100%
Saratoga82331June 12September 783 d100%
Sundance82729May 21September 25124 d100%

50% dates from NOAA NCEI U.S. Climate Normals 1991–2020, one row per station; a state page is published when at least 5 stations stand behind its pages. Where a freeze comes in fewer than nine winters in ten, the dates describe the winters that have one.