Frost dates in Wyoming
Across Wyoming, the typical last spring frost is around May 22 and the first fall frost around Sep 23. Your own dates depend on where you are in the state; find your county below.
Most of the state's last spring frosts fall between May 11 and Jun 14, and its first fall frosts between Sep 1 and Oct 1.
These are the dates with a 50% chance of a 32°F frost on or after (spring) or on or before (fall), so plan tender crops a week or two after the spring date and keep row cover handy. For dates at your exact ZIP code, use the zone and frost date lookup; for what to plant when, see the planting guide by frost date.
Hardiness zones in Wyoming: zone 4a, zone 4b, zone 5a, zone 5b
Frost dates by county in Wyoming
| County | Last spring frost | First fall frost | Growing season |
|---|---|---|---|
| Albany | Jun 1 | Sep 19 | About 110 days |
| Big Horn | May 9 | Sep 29 | About 143 days |
| Campbell | May 21 | Sep 23 | About 125 days |
| Carbon | Jun 1 | Sep 18 | About 109 days |
| Converse | May 23 | Sep 22 | About 122 days |
| Crook | May 21 | Sep 23 | About 125 days |
| Fremont | May 21 | Sep 24 | About 126 days |
| Goshen | May 14 | Sep 28 | About 137 days |
| Hot Springs | May 29 | Sep 17 | About 111 days |
| Johnson | May 22 | Sep 22 | About 123 days |
| Laramie | May 16 | Sep 27 | About 134 days |
| Lincoln | Jun 20 | Sep 1 | About 73 days |
| Natrona | May 23 | Sep 22 | About 122 days |
| Niobrara | May 17 | Sep 28 | About 134 days |
| Park | May 27 | Sep 25 | About 121 days |
| Platte | May 18 | Sep 24 | About 129 days |
| Sheridan | May 24 | Sep 23 | About 122 days |
| Sublette | Jun 9 | Sep 14 | About 97 days |
| Sweetwater | May 24 | Sep 27 | About 126 days |
| Teton | Jun 20 | Aug 31 | About 72 days |
| Uinta | Jun 14 | Sep 9 | About 87 days |
| Washakie | May 22 | Oct 1 | About 132 days |
| Weston | May 20 | Sep 23 | About 126 days |
Source: NOAA NCEI U.S. Climate Normals 1991–2020, 50% probability of 32°F, from the weather station nearest each ZIP code; each county shows the middle value across its ZIP codes. Hills, valleys and cities can run a week or more earlier or later.