Last frost dates in Wyoming
129 NOAA weather stations in Wyoming have thirty years of frost records. The median station sees its last 32 °F night around May 20; across the state that ranges from Apr 28 to Jun 24, so pick the station nearest you rather than a state-wide figure.
| BASIN | Apr 28 | May 11 | Apr 15 | Oct 10 | 164 |
| GREYBULL S BIG HORN AP | May 4 | May 18 | Apr 22 | Oct 1 | 149 |
| WORLAND | May 4 | May 18 | Apr 23 | Oct 1 | 149 |
| BOYSEN DAM | May 5 | May 20 | Apr 23 | Oct 7 | 153 |
| THERMOPOLIS | May 5 | May 19 | Apr 23 | Oct 5 | 152 |
| DEAVER | May 6 | May 20 | Apr 26 | Oct 1 | 148 |
| COLONY | May 7 | May 21 | Apr 26 | Oct 3 | 149 |
| GUERNSEY 2NW | May 7 | May 21 | Apr 24 | Oct 6 | 152 |
| SHOSHONI | May 7 | May 18 | Apr 27 | Oct 3 | 145 |
| WHALEN DAM USBR | May 7 | May 24 | Apr 25 | Oct 3 | 146 |
| GLENDO RSVR USBR | May 9 | May 24 | Apr 27 | Oct 5 | 148 |
| LOVELL | May 9 | May 25 | Apr 27 | Sep 29 | 142 |
| PATHFINDER DAM | May 9 | May 23 | Apr 28 | Oct 7 | 148 |
| CASPER WWTP | May 10 | May 24 | Apr 30 | Sep 29 | 138 |
| PINE BLUFFS 1ESE | May 10 | May 24 | Apr 30 | Oct 1 | 142 |
| TENSLEEP 4NE | May 10 | May 26 | Apr 27 | Oct 1 | 141 |
| GREYBULL | May 11 | May 24 | Apr 30 | Sep 23 | 133 |
| GUERNSEY DAM #2 | May 11 | May 25 | Apr 29 | Oct 3 | 144 |
| TORRINGTON MUNI AP | May 11 | May 26 | Apr 30 | Sep 29 | 139 |
| CASPER 1SW | May 12 | May 26 | Apr 28 | Oct 1 | 143 |
| CHEYENNE | May 12 | May 26 | May 1 | Oct 1 | 141 |
| CODY | May 12 | May 27 | Apr 27 | Oct 1 | 140 |
| EMBLEM | May 12 | May 27 | Apr 30 | Sep 28 | 136 |
| RIVERTON | May 12 | May 26 | May 1 | Sep 24 | 132 |
| SEMINOE RSVR USBR | May 12 | May 25 | May 1 | Oct 4 | 143 |
| BUFFALO JOHNSON CO AP | May 13 | May 28 | Apr 28 | Oct 1 | 141 |
| LANDER 11 SSE | May 13 | Jun 1 | May 1 | Oct 2 | 140 |
| NEWCASTLE | May 13 | May 26 | Apr 30 | Oct 3 | 143 |
| WORLAND | May 13 | May 27 | May 2 | Sep 26 | 133 |
| ALBIN | May 14 | May 25 | May 2 | Oct 2 | 142 |
| BLACK MTN | May 14 | Jun 1 | Apr 29 | Oct 3 | 140 |
| CARPENTER 3N | May 14 | May 27 | May 4 | Sep 26 | 133 |
| CHEYENNE WFO | May 14 | May 28 | May 3 | Oct 1 | 139 |
| LA GRANGE | May 14 | May 29 | May 1 | Oct 1 | 137 |
| LEITER 9N | May 14 | May 29 | Apr 30 | Sep 30 | 137 |
| LUSK 25NE | May 14 | May 27 | May 2 | Oct 1 | 139 |
| OLD FT LARAMIE | May 14 | May 27 | May 3 | Sep 26 | 134 |
| PAVILLION | May 14 | May 29 | Apr 30 | Sep 30 | 139 |
| TORRINGTON EXP FARM | May 14 | May 28 | May 2 | Sep 24 | 130 |
| DULL CTR 1SE | May 15 | May 28 | May 3 | Sep 27 | 133 |
| GILLETTE 4SE | May 15 | May 27 | May 1 | Oct 1 | 136 |
| HEART MTN | May 15 | Jun 1 | May 1 | Sep 25 | 132 |
| YODER 5 W | May 15 | Jun 2 | May 3 | Sep 27 | 132 |
| PINE BLUFFS 5W | May 16 | Jun 1 | May 5 | Sep 27 | 132 |
| REDBIRD | May 16 | May 31 | May 4 | Sep 24 | 130 |
| RIVERTON | May 16 | May 31 | May 1 | Sep 28 | 133 |
| SHELL | May 16 | Jun 3 | May 4 | Sep 24 | 130 |
| BIG HORN | May 17 | May 31 | May 2 | Sep 28 | 132 |
| BUFFALO BILL DAM | May 17 | Jun 3 | May 1 | Oct 3 | 136 |
| HULETT | May 17 | May 30 | May 6 | Sep 23 | 128 |
| LANCE CREEK 11NNE | May 17 | Jun 3 | May 5 | Sep 25 | 129 |
| RAWLINS 1N | May 17 | May 31 | May 5 | Oct 2 | 138 |
| TORRINGTON 29N | May 17 | May 31 | May 6 | Sep 28 | 133 |
| CHUGWATER | May 18 | Jun 2 | May 5 | Sep 24 | 129 |
| CLARK 3NE | May 18 | Jun 4 | May 6 | Sep 22 | 125 |
| KAYCEE | May 18 | May 31 | May 5 | Sep 25 | 129 |
| LANDER HUNT FLD AP | May 18 | Jun 3 | May 4 | Sep 27 | 131 |
| SHERIDAN FLD STN | May 18 | Jun 2 | May 4 | Sep 24 | 127 |
| BILLY CREEK | May 19 | May 31 | May 7 | Sep 21 | 123 |
| DOUGLAS 1 SE | May 19 | Jun 2 | May 7 | Sep 23 | 126 |
| POWELL FLD STN | May 19 | Jun 4 | May 5 | Sep 20 | 123 |
| WHEATLAND 4 N | May 19 | Jun 2 | May 7 | Sep 22 | 125 |
| LEO 6 SW | May 20 | Jun 13 | May 3 | Sep 28 | 128 |
| LINGLE 2WSW | May 20 | Jun 7 | May 8 | Sep 22 | 122 |
| UPTON | May 20 | Jun 4 | May 8 | Sep 23 | 123 |
| ARCHER | May 21 | Jun 6 | May 8 | Sep 24 | 124 |
| DIVERSION DAM | May 21 | Jun 6 | May 7 | Sep 20 | 119 |
| ECHETA 2 NW | May 21 | Jun 3 | May 9 | Sep 23 | 123 |
| MUDDY GAP | May 21 | Jun 10 | May 6 | Sep 27 | 126 |
| PHILLIPS | May 21 | Jun 7 | May 8 | Sep 21 | 121 |
| SHERIDAN CO AP | May 21 | Jun 6 | May 7 | Sep 23 | 123 |
| SUNDANCE | May 21 | Jun 5 | May 9 | Sep 25 | 124 |
| BATES CREEK #2 | May 22 | Jun 6 | May 8 | Sep 26 | 125 |
| GILLETTE CAMPBELL AP | May 22 | Jun 4 | May 8 | Sep 25 | 125 |
| LARAMIE 4SE | May 22 | Jun 4 | May 10 | Sep 28 | 126 |
| MIDWEST | May 22 | Jun 6 | May 8 | Sep 22 | 121 |
| MOORCROFT 3S | May 22 | Jun 9 | May 8 | Sep 28 | 127 |
| ROCK SPRINGS AP | May 22 | Jun 9 | May 5 | Sep 28 | 126 |
| SYBILLE RSCH UNIT | May 22 | Jun 5 | May 8 | Sep 24 | 125 |
| TENSLEEP 16SSE | May 22 | Jun 7 | May 10 | Sep 18 | 117 |
| DEVILS TWR #2 | May 23 | Jun 6 | May 12 | Sep 20 | 118 |
| DOUGLAS CONVERSE CO AP | May 23 | Jun 7 | May 10 | Sep 22 | 122 |
| LUSK 2 SW | May 23 | Jun 8 | May 9 | Sep 20 | 119 |
| POWDER RIVER #2 | May 23 | Jun 5 | May 9 | Sep 20 | 121 |
| SUNDANCE 8 NNW | May 23 | Jun 3 | May 10 | Sep 24 | 121 |
| WESTON 1 E | May 23 | Jun 5 | May 11 | Sep 18 | 118 |
| BUCKBOARD MARINA | May 24 | Jun 8 | May 11 | Sep 23 | 118 |
| BUFFALO | May 24 | Jun 9 | May 12 | Sep 21 | 118 |
| CLEARMONT 5 SW | May 24 | Jun 8 | May 12 | Sep 16 | 114 |
| CODY 12SE | May 24 | Jun 11 | May 10 | Sep 15 | 114 |
| DAYTON | May 24 | Jun 7 | May 11 | Sep 18 | 114 |
| GREEN RVR | May 24 | Jun 10 | May 7 | Sep 22 | 120 |
| ROCK SPRINGS FIRE DEPT | May 24 | Jun 9 | May 8 | Sep 24 | 121 |
| STORY | May 24 | Jun 9 | May 10 | Sep 23 | 120 |
| THERMOPOLIS 9NE | May 24 | Jun 9 | May 12 | Sep 16 | 112 |
| CHURCH BUTTES GAS PLT | May 25 | Jun 11 | May 8 | Sep 27 | 124 |
| DILLINGER | May 25 | Jun 8 | May 13 | Sep 17 | 113 |
| GLENDO 6NE | May 25 | Jun 11 | May 13 | Sep 15 | 112 |
| ROCHELLE 7ENE | May 25 | Jun 11 | May 11 | Sep 14 | 110 |
| WRIGHT 12W | May 25 | Jun 8 | May 14 | Sep 23 | 120 |
| CASPER NATRONA CO AP | May 26 | Jun 10 | May 12 | Sep 22 | 117 |
| HECLA 1E | May 27 | Jun 13 | May 12 | Sep 19 | 115 |
| WAPITI 1WSW | May 27 | Jun 12 | May 11 | Sep 25 | 121 |
| ELK MTN | May 28 | Jun 13 | May 14 | Sep 13 | 108 |
| CODY 21 SW | May 29 | Jun 17 | May 11 | Sep 18 | 110 |
| THERMOPOLIS 21WNW | May 29 | Jun 19 | May 14 | Sep 17 | 110 |
| POWDER RVR (SCHOOL) | May 30 | Jun 13 | May 12 | Sep 22 | 115 |
| BAGGS | Jun 1 | Jun 18 | May 15 | Sep 18 | 108 |
| BITTER CREEK 4 NE | Jun 1 | Jun 21 | May 15 | Sep 16 | 106 |
| BURRIS | Jun 1 | Jun 19 | May 17 | Sep 14 | 104 |
| JEFFREY CITY | Jun 1 | Jun 16 | May 17 | Sep 13 | 104 |
| MEDICINE BOW | Jun 1 | Jun 19 | May 20 | Sep 8 | 97 |
| RAWLINS MUNI AP | Jun 1 | Jun 17 | May 17 | Sep 15 | 105 |
| CENTENNIAL 1NE | Jun 2 | Jun 20 | May 22 | Sep 19 | 106 |
| DOUBLE FOUR RCH | Jun 2 | Jun 25 | May 18 | Sep 9 | 99 |
| LARAMIE RGNL AP | Jun 2 | Jun 18 | May 21 | Sep 15 | 102 |
| SARATOGA | Jun 2 | Jun 21 | May 15 | Sep 12 | 101 |
| EVANSTON BURNS FLD | Jun 3 | Jun 17 | May 16 | Sep 25 | 113 |
| YELLOWSTONE PARK MAMMOTH | Jun 3 | Jun 19 | May 18 | Sep 14 | 102 |
| WAMSUTTER | Jun 5 | Jun 23 | May 20 | Sep 14 | 101 |
| LARAMIE 2 NW | Jun 7 | Jun 29 | May 23 | Sep 4 | 88 |
| LA BARGE | Jun 9 | Jun 27 | May 24 | Sep 4 | 84 |
| EVANSTON 1 E | Jun 12 | Jul 2 | May 26 | Sep 12 | 90 |
| SARATOGA 4N | Jun 12 | Jun 30 | May 25 | Sep 7 | 83 |
| ALTA 1 NNW | Jun 14 | Jul 4 | May 23 | Sep 11 | 85 |
| MTN VIEW | Jun 14 | Jul 1 | May 31 | Sep 9 | 84 |
| AFTON | Jun 20 | Jul 7 | Jun 2 | Sep 1 | 71 |
| MOOSE | Jun 20 | Jul 9 | Jun 5 | Aug 31 | 70 |
| MOOSE 1 NNE | Jun 24 | Jul 11 | Jun 8 | Aug 28 | 63 |
How to read the three dates
Average is the date by which, in half of the years between 1991 and 2020, the last 32 °F night had already happened. Safe is later: only one year in ten saw a frost after it, which is the date to set out frost-tender plants such as dahlia tubers and zinnia seedlings. Early is the risky end, with a frost after it in nine years out of ten.
Every figure is for the weather station, not for your garden. A valley bottom, a north slope or a spot near a lake can run a week or two either way. Cities are warmer than the countryside around them.
Where the numbers come from
The dates are NOAA's U.S. Climate Normals for 1991 to 2020, computed by the National Centers for Environmental Information for every station with thirty years of daily minimum temperatures. ZIP codes are matched to the nearest such station within 150 km using U.S. Census Bureau ZIP Code Tabulation Area centroids. Stations that never see a frost, such as much of south Florida, report no date and are left out.