Frost dates by state › Wyoming
Wyoming frost dates
Average last spring and first fall frost dates for Wyoming’s largest cities, with each city’s USDA hardiness zone.
Reviewed October 2026
Among Wyoming’s 20 largest cities, the average last spring frost ranges from May 4 in Worland to Jun 12 in Evanston. Elevation, distance from the coast and city heat all shift the date, so use your own ZIP code below for the closest match.
In Jackson, the nearest weather station can record a freeze in any month, so pick fast, cold-tolerant crops and keep covers ready.
| City | Average last spring frost | Average first fall frost | Frost-free days | Hardiness zone | Weather station used |
|---|---|---|---|---|---|
| Cheyenne | May 14 | Oct 1 | 140 | 5b | Cheyenne Wfo, WY, 2 mi |
| Casper | May 10 | Sep 29 | 142 | 5a | Casper Wwtp, WY, 2 mi |
| Gillette | May 15 | Oct 1 | 139 | 4b | Gillette 4Se, WY, 3 mi |
| Laramie | Jun 7 | Sep 4 | 89 | 4a | Laramie 2 Nw, WY, 2 mi |
| Rock Springs | May 24 | Sep 24 | 123 | 5a | Rock Springs Fire Dept, WY, 2 mi |
| Sheridan | May 21 | Sep 23 | 125 | 5a | Sheridan Co Airport, WY, 2 mi |
| Evanston | Jun 12 | Sep 12 | 92 | 5a | Evanston 1 E, WY |
| Green River | May 24 | Sep 22 | 121 | 5a | Green Rvr, WY |
| Riverton | May 12 | Sep 24 | 135 | 5a | Riverton, WY |
| Jackson | Any month | Any month | – | 4b | Jackson, WY |
| Cody | May 12 | Oct 1 | 142 | 5a | Cody, WY, 3 mi |
| Rawlins | May 17 | Oct 2 | 138 | 5a | Rawlins 1N, WY, 2 mi |
| Lander | May 18 | Sep 27 | 132 | 5a | Lander Hunt Fld Airport, WY |
| Powell | May 19 | Sep 20 | 124 | 5a | Powell Fld Stn, WY |
| Douglas | May 19 | Sep 23 | 127 | 5a | Douglas 1 Se, WY, 2 mi |
| Torrington | May 11 | Sep 29 | 141 | 5a | Torrington Muni Airport, WY |
| Worland | May 4 | Oct 1 | 150 | 4b | Worland, WY |
| Buffalo | May 24 | Sep 21 | 120 | 5a | Buffalo, WY |
| Mills | May 26 | Sep 22 | 119 | 5a | Casper Natrona Co Airport, WY, 5 mi |
| Wheatland | May 19 | Sep 22 | 126 | 5a | Wheatland 4 N, WY, 4 mi |
Frost dates are the dates after (spring) or before (fall) which the chance of a 32°F freeze is below 50%, from NOAA’s 1991–2020 U.S. Climate Normals for the weather station nearest each city’s center. Zones are from the 2023 USDA Plant Hardiness Zone Map for the ZIP codes around each city; a range means nearby ZIP codes differ. Cities are the 20 largest by Census Bureau 2024 population estimates.
An average is not a guarantee. There’s still about a 1 in 2 chance of frost after the average last spring date. Many gardeners wait an extra week or two before setting out tomatoes, peppers and basil, and keep covers handy.
Planting dates for Cheyenne
Timed from Cheyenne’s average last frost of May 14, using University of New Hampshire Extension’s planting guidance. For your exact dates, enter your ZIP code in the calendar below.
| Crop | Start seeds indoors | Plant outside |
|---|---|---|
| Tomatoes | Mar 26 to Apr 9 | May 21 to May 28 |
| Peppers | Mar 19 to Apr 2 | May 28 |
| Lettuce | Mar 12 to Mar 19 | Apr 16 to Apr 23 |
| Broccoli | Mar 5 to Mar 19 | Apr 16 to Apr 30 |
| Cucumbers | Apr 23 to Apr 30 | May 21 to May 28 |
| Basil | Apr 2 to Apr 16 | May 28 |
When to plant, for your garden
Your seed-starting and planting dates, timed from your last spring frost. Full calendar, 12 crops.
Enter your ZIP code to look up your average last frost date and hardiness zone, or type the date in yourself.
Frost dates: NOAA U.S. Climate Normals, 1991–2020. Hardiness zones: USDA Plant Hardiness Zone Map, 2023, ZIP code data from PRISM Group, Oregon State University, prism.oregonstate.edu, accessed Oct. 20, 2026.
More about frost dates
How to find your last frost date, and what your zone means · Full planting calendar · How to start seeds indoors
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