Wyoming frost dates
The typical last spring frost ranges from May 12 in Cheyenne to Jun 24 in Jackson.
4 of the 4 Wyoming cities listed have typical frost dates. The longest frost-free season is 141 days in Cheyenne; the shortest is 63 days in Jackson. For a single address, look up your ZIP code: rural ZIPs use their nearest suitable station.
| City | Last spring frost | 1 in 10 after | First fall frost | 1 in 10 before | Hard freeze (28°F) | Season |
|---|---|---|---|---|---|---|
| Casper | May 26 | Jun 10 | Sep 22 | Sep 5 | May 11 / Oct 2 | 117 days |
| Cheyenne | May 12 | May 26 | Oct 1 | Sep 18 | May 2 / Oct 11 | 141 days |
| Gillette | May 22 | Jun 4 | Sep 25 | Sep 9 | May 9 / Oct 4 | 125 days |
| Jackson | Jun 24 | Jul 11 | Aug 28 | Aug 8 | Jun 7 / Sep 12 | 63 days |
Reading the table: Casper
In Casper, the last spring frost typically comes around May 26: in half of years it is earlier, in half later. In 1 year in 10 it comes after Jun 10, 15 days later, so tender plants set out after that date have a 90% chance of escaping frost. In fall, the first frost typically arrives around Sep 22, and in 1 year in 10 before Sep 5. Hard freezes (28°F) usually end earlier in spring and start later in fall: around May 11 and Oct 2 in Casper.
Frost dates at more Wyoming weather stations
NOAA stations across Wyoming used by our ZIP code lookup, named for the town they are in.
| Station | Elevation | Last spring frost | First fall frost |
|---|---|---|---|
| Afton | 6,248 ft | Jun 20 (1 in 10 after Jul 7) | Sep 1 (before Aug 12) |
| Albin | 5,345 ft | May 14 (1 in 10 after May 25) | Oct 2 (before Sep 18) |
| Alta 1 Nnw | 6,440 ft | Jun 14 (1 in 10 after Jul 4) | Sep 11 (before Aug 28) |
| Baggs | 6,319 ft | Jun 1 (1 in 10 after Jun 18) | Sep 18 (before Sep 4) |
| Basin | 3,840 ft | Apr 28 (1 in 10 after May 11) | Oct 10 (before Sep 26) |
| Burris | 6,125 ft | Jun 1 (1 in 10 after Jun 19) | Sep 14 (before Sep 1) |
| Carpenter 3N | 5,437 ft | May 14 (1 in 10 after May 27) | Sep 26 (before Sep 12) |
| Casper Wwtp | 5,097 ft | May 10 (1 in 10 after May 24) | Sep 29 (before Sep 14) |
| Chugwater | 5,304 ft | May 18 (1 in 10 after Jun 2) | Sep 24 (before Sep 9) |
| Church Buttes Gas Plt | 7,079 ft | May 25 (1 in 10 after Jun 11) | Sep 27 (before Sep 14) |
| Clark 3NE | 4,117 ft | May 18 (1 in 10 after Jun 4) | Sep 22 (before Sep 8) |
| Cody 21 Sw | 5,840 ft | May 29 (1 in 10 after Jun 17) | Sep 18 (before Sep 3) |
| Deaver | 4,105 ft | May 6 (1 in 10 after May 20) | Oct 1 (before Sep 19) |
| Devils Twr #2 | 3,862 ft | May 23 (1 in 10 after Jun 6) | Sep 20 (before Sep 4) |
| Dillinger | 4,310 ft | May 25 (1 in 10 after Jun 8) | Sep 17 (before Sep 3) |
| Diversion Dam | 5,578 ft | May 21 (1 in 10 after Jun 6) | Sep 20 (before Sep 5) |
| Douglas Converse Co Airport | 4,929 ft | May 23 (1 in 10 after Jun 7) | Sep 22 (before Sep 9) |
| Elk Mtn | 7,265 ft | May 28 (1 in 10 after Jun 13) | Sep 13 (before Aug 30) |
| Emblem | 4,448 ft | May 12 (1 in 10 after May 27) | Sep 28 (before Sep 14) |
| Glendo 6NE | 4,739 ft | May 25 (1 in 10 after Jun 11) | Sep 15 (before Sep 4) |
| Green Rvr | 6,160 ft | May 24 (1 in 10 after Jun 10) | Sep 22 (before Sep 7) |
| Heart Mtn | 4,790 ft | May 15 (1 in 10 after Jun 1) | Sep 25 (before Sep 11) |
| Hecla 1E | 6,690 ft | May 27 (1 in 10 after Jun 13) | Sep 19 (before Sep 3) |
| Hulett | 3,758 ft | May 17 (1 in 10 after May 30) | Sep 23 (before Sep 8) |
| Jeffrey City | 6,319 ft | Jun 1 (1 in 10 after Jun 16) | Sep 13 (before Sep 1) |
| Kaycee | 4,660 ft | May 18 (1 in 10 after May 31) | Sep 25 (before Sep 11) |
| La Barge | 6,598 ft | Jun 9 (1 in 10 after Jun 27) | Sep 4 (before Aug 21) |
| Lance Creek 11NNE | 4,204 ft | May 17 (1 in 10 after Jun 3) | Sep 25 (before Sep 9) |
| Laramie 4SE | 7,390 ft | May 22 (1 in 10 after Jun 4) | Sep 28 (before Sep 16) |
| Laramie Rgnl Airport | 7,266 ft | Jun 2 (1 in 10 after Jun 18) | Sep 15 (before Sep 3) |
| Leiter 9N | 4,160 ft | May 14 (1 in 10 after May 29) | Sep 30 (before Sep 17) |
| Lingle 2WSW | 4,158 ft | May 20 (1 in 10 after Jun 7) | Sep 22 (before Sep 8) |
| Lovell | 3,847 ft | May 9 (1 in 10 after May 25) | Sep 29 (before Sep 16) |
| Lusk 2 Sw | 5,090 ft | May 23 (1 in 10 after Jun 8) | Sep 20 (before Sep 4) |
| Lusk 25NE | 4,136 ft | May 14 (1 in 10 after May 27) | Oct 1 (before Sep 19) |
| Medicine Bow | 6,635 ft | Jun 1 (1 in 10 after Jun 19) | Sep 8 (before Aug 28) |
| Midwest | 4,860 ft | May 22 (1 in 10 after Jun 6) | Sep 22 (before Sep 8) |
| Mtn View | 6,800 ft | Jun 14 (1 in 10 after Jul 1) | Sep 9 (before Aug 23) |
| Muddy Gap | 6,248 ft | May 21 (1 in 10 after Jun 10) | Sep 27 (before Sep 12) |
| Newcastle | 4,415 ft | May 13 (1 in 10 after May 26) | Oct 3 (before Sep 17) |
| Old Ft Laramie | 4,250 ft | May 14 (1 in 10 after May 27) | Sep 26 (before Sep 12) |
| Pathfinder Dam | 5,923 ft | May 9 (1 in 10 after May 23) | Oct 7 (before Sep 22) |
| Phillips | 4,982 ft | May 21 (1 in 10 after Jun 7) | Sep 21 (before Sep 8) |
| Pine Bluffs 5W | 5,180 ft | May 16 (1 in 10 after Jun 1) | Sep 27 (before Sep 13) |
| Powder River #2 | 5,700 ft | May 23 (1 in 10 after Jun 5) | Sep 20 (before Sep 7) |
| Powell Fld Stn | 4,372 ft | May 19 (1 in 10 after Jun 4) | Sep 20 (before Sep 7) |
| Rawlins Muni Airport | 6,736 ft | Jun 1 (1 in 10 after Jun 17) | Sep 15 (before Sep 3) |
| Riverton | 4,955 ft | May 12 (1 in 10 after May 26) | Sep 24 (before Sep 11) |
| Rock Springs Airport | 6,741 ft | May 22 (1 in 10 after Jun 9) | Sep 28 (before Sep 14) |
| Saratoga | 6,790 ft | Jun 2 (1 in 10 after Jun 21) | Sep 12 (before Aug 12) |
| Seminoe Rsvr Usbr | 6,975 ft | May 12 (1 in 10 after May 25) | Oct 4 (before Sep 23) |
| Sheridan Co Airport | 3,945 ft | May 21 (1 in 10 after Jun 6) | Sep 23 (before Sep 9) |
| Sheridan Fld Stn | 3,750 ft | May 18 (1 in 10 after Jun 2) | Sep 24 (before Sep 9) |
| Shoshoni | 4,837 ft | May 7 (1 in 10 after May 18) | Oct 3 (before Sep 23) |
| Story | 5,168 ft | May 24 (1 in 10 after Jun 9) | Sep 23 (before Sep 8) |
| Torrington 29N | 4,860 ft | May 17 (1 in 10 after May 31) | Sep 28 (before Sep 15) |
| Torrington Muni Airport | 4,205 ft | May 11 (1 in 10 after May 26) | Sep 29 (before Sep 16) |
| Upton | 4,320 ft | May 20 (1 in 10 after Jun 4) | Sep 23 (before Sep 7) |
| Worland | 4,172 ft | May 13 (1 in 10 after May 27) | Sep 26 (before Sep 14) |
| Yoder 5 W | 4,330 ft | May 15 (1 in 10 after Jun 2) | Sep 27 (before Sep 12) |
32°F dates from NOAA 1991-2020 freeze probabilities for each city's station. "1 in 10 after": a 10% chance of a later spring frost (planting is 90% safe after it). How to read frost dates.