Wyoming Frost Dates: Last and First Frost by Town

158 NOAA weather stations · 1991–2020 U.S. Climate Normals · Data updated 2026-10-29

Quick answer

Across Wyoming's 129 NOAA stations with regular frost, the median last spring frost is May 20 and the median first fall frost is September 24. Last frost dates range from April 28 at Basin to June 24 at Moose 1 NNE, so enter your ZIP code below for the station nearest you.

How frost dates vary across Wyoming

Elevation matters: across Wyoming's stations, each 1,000 ft of elevation delays the median last frost by about 6 days.
Safety margin: the median 10%-risk date (June 4) is about 15 days after the median last frost. Waiting until then cuts the chance of a killing frost on tender transplants from 1 in 2 to 1 in 10.

Frost dates at Wyoming's major weather stations

These National Weather Service stations, mostly at airports, have the longest and most complete records in the state.


Big Piney Marbleton Airport	6,970	Any month	Any month	Any month	52
Buffalo Johnson County Airport	4,967	May 13	May 28	Oct 1	141
Casper Natrona County Airport	5,338	May 26	Jun 10	Sep 22	117
Cheyenne	6,128	May 12	May 26	Oct 1	141
Douglas Converse County Airport	4,929	May 23	Jun 7	Sep 22	122
Evanston Burns Field	7,163	Jun 3	Jun 17	Sep 25	113
Gillette Campbell Airport	4,354	May 22	Jun 4	Sep 25	125
Greybull S Big Horn Airport	3,933	May 4	May 18	Oct 1	149
Lander 11 SSE	5,773	May 13	Jun 1	Oct 2	140
Lander Hunt Field Airport	5,592	May 18	Jun 3	Sep 27	131
Laramie Regional Airport	7,266	Jun 2	Jun 18	Sep 15	102
Moorcroft 3S	4,325	May 22	Jun 9	Sep 28	127
Moose 1 NNE	6,466	Jun 24	Jul 11	Aug 28	63
Rawlins Municipal Airport	6,736	Jun 1	Jun 17	Sep 15	105
Riverton	5,568	May 16	May 31	Sep 28	133
Rock Springs Airport	6,741	May 22	Jun 9	Sep 28	126
Sheridan County Airport	3,945	May 21	Jun 6	Sep 23	123
Sundance 8 NNW	5,792	May 23	Jun 3	Sep 24	121
Torrington Municipal Airport	4,205	May 11	May 26	Sep 29	139
Worland	4,172	May 13	May 27	Sep 26	133
Yellowstone Lake	7,835	Any month	Any month	Any month	37

All 158 stations in Wyoming

Last frost and first frost are medians: a 50% chance of a 32°F night after (spring) or before (fall) that date. 10% risk is the spring date with only a 1-in-10 chance of a later frost. Click a column to sort.

Filter by station name


Afton	6,248	Jun 20	Jul 7	Sep 1	71
Albin	5,345	May 14	May 25	Oct 2	142
Alta 1 NNW	6,440	Jun 14	Jul 4	Sep 11	85
Archer	6,010	May 21	Jun 6	Sep 24	124
Atlantic City	7,821	Any month	Any month	Any month	66
Baggs	6,319	Jun 1	Jun 18	Sep 18	108
Basin	3,840	Apr 28	May 11	Oct 10	164
Bates Creek #2	6,042	May 22	Jun 6	Sep 26	125
Bedford 3 SE	6,355	Any month	Any month	Any month	67
Big Horn	4,208	May 17	May 31	Sep 28	132
Big Piney Marbleton Airport	6,970	Any month	Any month	Any month	52
Billy Creek	4,975	May 19	May 31	Sep 21	123
Bitter Creek 4 NE	6,722	Jun 1	Jun 21	Sep 16	106
Black Mountain	5,635	May 14	Jun 1	Oct 3	140
Bondurant	6,693	Any month	Any month	Any month	49
Boulder Rearing Station	6,940	Any month	Any month	Any month	43
Boysen Dam	4,875	May 5	May 20	Oct 7	153
Buckboard Marina	6,080	May 24	Jun 8	Sep 23	118
Buffalo	4,639	May 24	Jun 9	Sep 21	118
Buffalo Bill Dam	5,160	May 17	Jun 3	Oct 3	136
Buffalo Johnson County Airport	4,967	May 13	May 28	Oct 1	141
Burgess Junction	8,060	Any month	Any month	Any month	52
Burris	6,125	Jun 1	Jun 19	Sep 14	104
Carpenter 3N	5,437	May 14	May 27	Sep 26	133
Casper 1SW	5,143	May 12	May 26	Oct 1	143
Casper Natrona County Airport	5,338	May 26	Jun 10	Sep 22	117
Casper Wwtp	5,097	May 10	May 24	Sep 29	138
Centennial 1NE	8,170	Jun 2	Jun 20	Sep 19	106
Cheyenne	6,128	May 12	May 26	Oct 1	141
Cheyenne WFO	6,119	May 14	May 28	Oct 1	139
Chugwater	5,304	May 18	Jun 2	Sep 24	129
Church Buttes Gas Plt	7,079	May 25	Jun 11	Sep 27	124
Clark 3NE	4,117	May 18	Jun 4	Sep 22	125
Clearmont 5 SW	3,995	May 24	Jun 8	Sep 16	114
Cody	5,280	May 12	May 27	Oct 1	140
Cody 12SE	5,248	May 24	Jun 11	Sep 15	114
Cody 21 SW	5,840	May 29	Jun 17	Sep 18	110
Colony	3,480	May 7	May 21	Oct 3	149
Cora	7,347	Any month	Any month	Any month	35
Daniel Fish Hatchery	7,341	Any month	Any month	Any month	19
Darwin Rch	8,190	Any month	Any month	Any month	17
Dayton	3,920	May 24	Jun 7	Sep 18	114
Deaver	4,105	May 6	May 20	Oct 1	148
Devils Tower #2	3,862	May 23	Jun 6	Sep 20	118
Dillinger	4,310	May 25	Jun 8	Sep 17	113
Diversion Dam	5,578	May 21	Jun 6	Sep 20	119
Double Four Rch	6,120	Jun 2	Jun 25	Sep 9	99
Douglas 1 SE	4,870	May 19	Jun 2	Sep 23	126
Douglas Converse County Airport	4,929	May 23	Jun 7	Sep 22	122
Dubois	6,955	Any month	Any month	Any month	74
Dull Center 1SE	4,415	May 15	May 28	Sep 27	133
Echeta 2 NW	4,000	May 21	Jun 3	Sep 23	123
Elk Mountain	7,265	May 28	Jun 13	Sep 13	108
Emblem	4,448	May 12	May 27	Sep 28	136
Evanston 1 E	6,825	Jun 12	Jul 2	Sep 12	90
Evanston Burns Field	7,163	Jun 3	Jun 17	Sep 25	113
Farson 2NNE	6,620	Any month	Any month	Any month	84
Fontenelle Dam	6,485	Any month	Any month	Any month	69
Fossil Butte	6,785	Any month	Any month	Any month	43
Gillette 4SE	4,640	May 15	May 27	Oct 1	136
Gillette Campbell Airport	4,354	May 22	Jun 4	Sep 25	125
Glendo 6NE	4,739	May 25	Jun 11	Sep 15	112
Glendo Rsvr Usbr	4,780	May 9	May 24	Oct 5	148
Green River	6,160	May 24	Jun 10	Sep 22	120
Greybull	3,787	May 11	May 24	Sep 23	133
Greybull S Big Horn Airport	3,933	May 4	May 18	Oct 1	149
Guernsey 2NW	4,480	May 7	May 21	Oct 6	152
Guernsey Dam #2	4,355	May 11	May 25	Oct 3	144
Heart Mountain	4,790	May 15	Jun 1	Sep 25	132
Hecla 1E	6,690	May 27	Jun 13	Sep 19	115
Hulett	3,758	May 17	May 30	Sep 23	128
Jackson	6,210	Any month	Any month	Any month	46
Jeffrey City	6,319	Jun 1	Jun 16	Sep 13	104
Kaycee	4,660	May 18	May 31	Sep 25	129
Kemmerer 2N	6,937	Any month	Any month	Any month	66
La Barge	6,598	Jun 9	Jun 27	Sep 4	84
La Grange	4,590	May 14	May 29	Oct 1	137
Lake Yellowstone	7,892	Any month	Any month	Any month	64
Lamar Ranger Station	6,575	Any month	Any month	Any month	51
Lance Creek 11NNE	4,204	May 17	Jun 3	Sep 25	129
Lander 11 SSE	5,773	May 13	Jun 1	Oct 2	140
Lander Hunt Field Airport	5,592	May 18	Jun 3	Sep 27	131
Laramie 2 NW	7,140	Jun 7	Jun 29	Sep 4	88
Laramie 4SE	7,390	May 22	Jun 4	Sep 28	126
Laramie Regional Airport	7,266	Jun 2	Jun 18	Sep 15	102
Leiter 9N	4,160	May 14	May 29	Sep 30	137
Leo 6 SW	6,035	May 20	Jun 13	Sep 28	128
Lingle 2WSW	4,158	May 20	Jun 7	Sep 22	122
Lovell	3,847	May 9	May 25	Sep 29	142
Lusk 2 SW	5,090	May 23	Jun 8	Sep 20	119
Lusk 25NE	4,136	May 14	May 27	Oct 1	139
Medicine Bow	6,635	Jun 1	Jun 19	Sep 8	97
Midwest	4,860	May 22	Jun 6	Sep 22	121
Moorcroft 3S	4,325	May 22	Jun 9	Sep 28	127
Moose	6,444	Jun 20	Jul 9	Aug 31	70
Moose 1 NNE	6,466	Jun 24	Jul 11	Aug 28	63
Moran 5WNW	6,805	Any month	Any month	Any month	61
Mountain View	6,800	Jun 14	Jul 1	Sep 9	84
Muddy Gap	6,248	May 21	Jun 10	Sep 27	126
Newcastle	4,415	May 13	May 26	Oct 3	143
Old Faithful	7,351	Any month	Any month	Any month	28
Old Fort Laramie	4,250	May 14	May 27	Sep 26	134
Pahaska	6,692	Any month	Any month	Any month	49
Pathfinder Dam	5,923	May 9	May 23	Oct 7	148
Pavillion	5,480	May 14	May 29	Sep 30	139
Phillips	4,982	May 21	Jun 7	Sep 21	121
Pine Bluffs 1ESE	5,058	May 10	May 24	Oct 1	142
Pine Bluffs 5W	5,180	May 16	Jun 1	Sep 27	132
Pinedale	7,210	Any month	Any month	Any month	58
Powder River (school)	5,722	May 30	Jun 13	Sep 22	115
Powder River #2	5,700	May 23	Jun 5	Sep 20	121
Powell Field Station	4,372	May 19	Jun 4	Sep 20	123
Rawlins 1N	6,908	May 17	May 31	Oct 2	138
Rawlins Municipal Airport	6,736	Jun 1	Jun 17	Sep 15	105
Redbird	3,890	May 16	May 31	Sep 24	130
Riverton	4,955	May 12	May 26	Sep 24	132
Riverton	5,568	May 16	May 31	Sep 28	133
Rochelle 7ENE	4,239	May 25	Jun 11	Sep 14	110
Rock Springs Airport	6,741	May 22	Jun 9	Sep 28	126
Rock Springs Fire Dept	6,270	May 24	Jun 9	Sep 24	121
Sage 4 NNW	6,210	Any month	Any month	Any month	62
Saratoga	6,790	Jun 2	Jun 21	Sep 12	101
Saratoga 4N	6,801	Jun 12	Jun 30	Sep 7	83
Seminoe Rsvr Usbr	6,975	May 12	May 25	Oct 4	143
Shell	4,242	May 16	Jun 3	Sep 24	130
Sheridan County Airport	3,945	May 21	Jun 6	Sep 23	123
Sheridan Field Station	3,750	May 18	Jun 2	Sep 24	127
Shirley Basin	7,057	Any month	Any month	Any month	75
Shoshoni	4,837	May 7	May 18	Oct 3	145
Snake River	6,882	Any month	Any month	Any month	23
South Pass City	7,840	Any month	Any month	Any month	43
Story	5,168	May 24	Jun 9	Sep 23	120
Sundance	4,695	May 21	Jun 5	Sep 25	124
Sundance 8 NNW	5,792	May 23	Jun 3	Sep 24	121
Sunshine 3NE	6,224	Any month	Any month	Any month	80
Sybille Rsch Unit	6,086	May 22	Jun 5	Sep 24	125
Tensleep 16SSE	4,680	May 22	Jun 7	Sep 18	117
Tensleep 4NE	4,748	May 10	May 26	Oct 1	141
Thermopolis	4,321	May 5	May 19	Oct 5	152
Thermopolis 21WNW	5,510	May 29	Jun 19	Sep 17	110
Thermopolis 9NE	4,282	May 24	Jun 9	Sep 16	112
Torrington 29N	4,860	May 17	May 31	Sep 28	133
Torrington Experiment Farm	4,098	May 14	May 28	Sep 24	130
Torrington Municipal Airport	4,205	May 11	May 26	Sep 29	139
Tower Falls	6,275	Any month	Any month	Any month	49
Upton	4,320	May 20	Jun 4	Sep 23	123
Wamsutter	6,740	Jun 5	Jun 23	Sep 14	101
Wapiti 1WSW	5,558	May 27	Jun 12	Sep 25	121
Weston 1 E	3,738	May 23	Jun 5	Sep 18	118
Whalen Dam Usbr	4,294	May 7	May 24	Oct 3	146
Wheatland 4 N	4,638	May 19	Jun 2	Sep 22	125
Worland	4,058	May 4	May 18	Oct 1	149
Worland	4,172	May 13	May 27	Sep 26	133
Wright 12W	5,020	May 25	Jun 8	Sep 23	120
Yellowstone Lake	7,835	Any month	Any month	Any month	37
Yellowstone National Park E Ent	6,954	Any month	Any month	Any month	43
Yellowstone Park Mammoth	6,195	Jun 3	Jun 19	Sep 14	102
Yoder 5 W	4,330	May 15	Jun 2	Sep 27	132

Frequently asked questions

When is the last frost in Wyoming?

The median last spring frost (32°F) across Wyoming's NOAA weather stations is May 20, based on 1991–2020 climate normals. It ranges from April 28 at Basin to June 24 at Moose 1 NNE. For a safer planting date, use the 10%-risk date; the state median for that is June 4.

When is the first frost in Wyoming?

The median first fall frost across Wyoming's stations is September 24. The earliest median first frost is August 28 at Moose 1 NNE, and the latest is October 10 at Basin.

How long is the growing season in Wyoming?

The median frost-free season is 125 days across Wyoming's stations, from 63 days at Moose 1 NNE to 164 days at Basin.

When should I plant tomatoes in Wyoming?

Plant tomatoes outdoors after your local last frost, ideally after the 10%-risk date when nights stay above 50°F. At a typical Wyoming station that means starting seeds indoors 6–8 weeks before May 20 and transplanting from about June 4. Check your ZIP code, because dates vary by weeks across the state.

Can it frost in summer in Wyoming?

Yes, at 29 stations in Wyoming a 32°F night is possible in any month, mostly at high elevation or far north. There is no reliable frost-free season there; use cold-hardy crops and row covers.

How to use these dates

Frost dates are 30-year averages from NOAA, not forecasts. Use them to plan seed starting and planting, then watch the 10-day forecast as the date approaches. Cold air settles in valleys and low spots, so a garden at the bottom of a slope can frost a week or more later in spring than the nearest station shows.

Ready to plan? The planting calendar by ZIP code turns these dates into start-indoors, transplant and sowing dates for 30 crops.

Sources and method

Dates are the 32°F freeze probabilities published in the NOAA NCEI 1991–2020 U.S. Climate Normals for each station. Station names are NOAA's, lightly expanded for readability. See the methodology or download the full table.