Idaho Frost Dates: Last and First Frost by Town

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

Quick answer

Across Idaho's 127 NOAA stations with regular frost, the median last spring frost is May 16 and the median first fall frost is September 29. Last frost dates range from April 2 at Brownlee Dam to June 22 at McCall, so enter your ZIP code below for the station nearest you.

How frost dates vary across Idaho

Elevation matters: across Idaho's stations, each 1,000 ft of elevation delays the median last frost by about 10 days.
Safety margin: the median 10%-risk date (June 4) is about 19 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 Idaho's major weather stations

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


Arco 17 SW	5,920	May 24	Jun 15	Oct 1	130
Boise Air Terminal	2,814	Apr 24	May 9	Oct 21	179
Burley Municipal Airport	4,142	May 7	May 23	Oct 4	150
Challis Airport	5,033	May 14	Jun 2	Sep 25	131
Idaho Falls 46 W	4,938	Jun 11	Jul 1	Sep 6	89
Idaho Falls Fanning Field	4,729	May 23	Jun 13	Sep 20	114
Jerome County Airport	4,048	May 1	May 16	Oct 14	165
Lewiston Nez Perce County Airport	1,436	Apr 6	Apr 26	Oct 26	200
Lowell Three Rivers	1,480	Apr 16	May 4	Oct 25	191
Malad City	4,470	May 22	Jun 16	Sep 20	116
McCall Airport	5,013	Jun 10	Jun 28	Sep 10	93
Mullan Pass Vor/dme	6,028	Jun 10	Jun 25	Sep 23	104
Murphy 10 W	3,950	May 17	Jun 6	Sep 30	134
Pocatello Regional Airport	4,478	May 23	Jun 13	Sep 18	117
Rexburg Madison County Airport	4,858	May 15	Jun 3	Sep 23	129
Stanley Ranger Station	6,495	Any month	Any month	Any month	29
Twin Falls Sun Valley Regional Airport	4,151	May 9	May 28	Oct 4	147

All 144 stations in Idaho

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


Aberdeen Experiment Station	4,405	May 21	Jun 13	Sep 20	118
American Falls	4,510	May 4	May 21	Oct 8	155
American Falls 6 NE	4,415	May 14	Jun 4	Oct 2	138
Arco	5,325	May 22	Jun 9	Sep 22	119
Arco 17 SW	5,920	May 24	Jun 15	Oct 1	130
Arrowrock Dam	3,235	Apr 28	May 16	Oct 14	169
Ashton 1N	5,212	May 21	Jun 13	Sep 21	121
Bayview Model Basin	2,087	May 22	Jun 6	Sep 22	122
Bellevue	5,192	May 13	Jun 3	Oct 2	139
Bern	5,964	Jun 17	Jul 4	Sep 3	77
Blackfoot Fire Dept	4,499	May 5	May 22	Oct 3	149
Boise 7 N	3,885	May 17	Jun 10	Oct 12	147
Boise Air Terminal	2,814	Apr 24	May 9	Oct 21	179
Boise Lucky Peak Dam	2,840	Apr 30	May 18	Oct 22	173
Bonners Ferry	2,075	Apr 30	May 16	Oct 4	154
Brownlee Dam	1,844	Apr 2	Apr 20	Nov 5	216
Bruneau	2,530	Apr 17	May 7	Oct 17	181
Buhl #2	3,800	Apr 25	May 10	Oct 15	172
Burley Municipal Airport	4,142	May 7	May 23	Oct 4	150
Cabinet Gorge	2,173	May 9	May 25	Oct 8	153
Cambridge	2,650	May 15	Jun 4	Sep 27	134
Cascade 1 NW	4,896	May 30	Jun 21	Sep 19	110
Castleford 2 N	3,825	May 17	Jun 5	Sep 29	132
Challis Airport	5,033	May 14	Jun 2	Sep 25	131
Chilly Barton Flat	6,260	Jun 14	Jun 30	Sep 8	86
Coeur D'alene	2,133	Apr 22	May 6	Oct 18	179
Cottonwood 2 WSW	3,945	May 6	May 26	Oct 13	156
Council	2,943	May 10	Jun 1	Oct 2	145
Craters Of The Moon	5,914	Jun 19	Jul 2	Sep 9	81
Deadwood Lodge	5,948	Any month	Any month	Any month	32
Deer Flat Dam	2,510	Apr 23	May 9	Oct 18	178
Dixie	5,620	Any month	Any month	Any month	29
Dixie N	5,740	Any month	Any month	Any month	30
Downey	4,865	May 31	Jun 16	Sep 18	110
Driggs	6,120	Jun 13	Jun 28	Sep 9	86
Dubois Experiment Station	5,450	May 18	Jun 9	Sep 30	132
Dworshak Fish Hatchery	995	Apr 20	May 5	Oct 20	182
Elk City 1NE	4,058	Any month	Any month	Any month	64
Elk River	2,866	May 16	Jun 1	Sep 23	128
Emmett 2 E	2,390	Apr 30	May 17	Oct 17	168
Fairfield Ranger Station	5,065	Jun 8	Jun 28	Sep 14	97
Fenn Ranger Station	1,560	Apr 26	May 9	Oct 20	176
Fort Hall 1 NNE	4,465	May 20	Jun 12	Sep 20	119
Garden Valley	3,100	Jun 1	Jun 20	Sep 10	102
Gibbonsville #2	4,480	Jun 1	Jun 19	Sep 17	107
Glenns Ferry	2,466	May 1	May 16	Oct 3	154
Grace	5,550	May 29	Jun 16	Sep 17	111
Grand View 4 NW	2,400	Apr 28	May 13	Oct 6	162
Grangeville	3,300	May 9	May 27	Oct 3	146
Hagerman 2 SW	2,897	May 3	May 17	Oct 1	151
Hamer 4 NW	4,790	Jun 3	Jun 21	Sep 11	98
Hazelton	4,060	May 7	May 26	Oct 5	149
Headquarters	3,200	Any month	Any month	Any month	81
Hill City 1 W	5,100	Jun 16	Jul 3	Sep 6	80
Homedale 1 SE	2,230	Apr 24	May 5	Oct 9	169
Howe	4,820	May 24	Jun 14	Sep 14	113
Idaho City	3,965	Jun 17	Jul 4	Sep 5	80
Idaho Falls - Kifi	4,742	May 9	Jun 2	Oct 1	142
Idaho Falls 16 SE	5,828	Jun 9	Jun 26	Sep 11	93
Idaho Falls 46 W	4,938	Jun 11	Jul 1	Sep 6	89
Idaho Falls Fanning Field	4,729	May 23	Jun 13	Sep 20	114
Island Park	6,290	Any month	Any month	Any month	49
Jerome	3,740	May 2	May 30	Oct 14	166
Jerome County Airport	4,048	May 1	May 16	Oct 14	165
Kamiah	1,210	Apr 29	May 12	Oct 5	163
Kellogg	2,377	May 14	Jun 3	Sep 26	131
Ketchum Ranger Station	5,890	Any month	Any month	Any month	77
Kooskia 5 SSE	2,330	Apr 30	May 13	Oct 11	162
Lava Hot Springs	4,595	May 21	Jun 11	Sep 21	118
Leadore #2	6,000	Any month	Any month	Any month	50
Lewiston Nez Perce County Airport	1,436	Apr 6	Apr 26	Oct 26	200
Lifton Pumping Station	5,935	May 19	Jun 5	Sep 21	123
Lowell Three Rivers	1,480	Apr 16	May 4	Oct 25	191
Lowman	3,920	Jun 6	Jul 1	Sep 4	87
Mackay Lost River Ranger Station	5,897	Jun 1	Jun 21	Sep 20	109
Malad City	4,470	May 22	Jun 16	Sep 20	116
Malta	4,521	Jun 5	Jun 23	Sep 13	96
Malta 4 ESE	4,590	Jun 1	Jun 19	Sep 19	111
Massacre Rocks State Park	4,195	May 20	Jun 9	Sep 26	125
May 2SSE	5,050	Jun 12	Jun 29	Sep 6	85
McCall	5,025	Jun 22	Jul 10	Sep 2	72
McCall Airport	5,013	Jun 10	Jun 28	Sep 10	93
McCammon	4,770	May 23	Jun 10	Sep 24	121
Middle Fork Lodge	4,480	May 21	Jun 13	Sep 18	115
Minidoka Dam	4,164	May 16	Jun 5	Oct 1	136
Monteview	4,815	Jun 12	Jun 30	Sep 7	87
Moscow U Of I	2,660	Any month	Any month	Any month	85
Mountain Home	3,140	May 2	May 23	Oct 8	157
Mullan	3,201	May 12	Jun 19	Sep 30	138
Mullan Pass Vor/dme	6,028	Jun 10	Jun 25	Sep 23	104
Murphy (desert) Hot Springs	5,152	Any month	Any month	Any month	87
Murphy 10 W	3,950	May 17	Jun 6	Sep 30	134
Nampa Sugar Factory	2,470	Apr 29	May 18	Oct 13	164
New Meadows Ranger Station	3,862	Any month	Any month	Any month	62
Nezperce	3,248	May 24	Jun 19	Sep 20	116
Oakley	4,559	May 15	Jun 6	Oct 2	137
Ola	3,075	May 31	Jun 19	Sep 16	108
Parma Experiment Station	2,290	Apr 27	May 9	Oct 9	165
Paul 1ENE	4,150	May 6	May 22	Oct 6	151
Payette	2,150	Apr 19	May 5	Oct 20	183
Picabo	4,839	Jun 16	Jun 30	Sep 9	85
Pierce	3,080	Jun 3	Jun 29	Sep 7	93
Plummer 3 WSW	2,905	May 11	Jun 4	Oct 5	143
Pocatello 2 NE	4,832	May 16	Jun 6	Oct 2	137
Pocatello City	4,460	May 2	May 18	Oct 11	161
Pocatello Regional Airport	4,478	May 23	Jun 13	Sep 18	117
Porthill 1 SW	1,799	May 4	May 28	Sep 30	145
Potlatch 3 NNE	2,760	May 15	Jun 2	Sep 21	126
Powell	3,530	May 31	Jun 26	Sep 12	102
Preston	4,719	May 16	Jun 4	Sep 28	133
Prichard 3 ESE	2,547	May 31	Jun 23	Sep 5	95
Priest River Experiment Station	2,371	May 20	Jun 4	Sep 13	114
Red River Ranger Station	4,350	Any month	Any month	Any month	59
Rexburg Byu Idaho	5,005	May 12	Jun 2	Sep 24	132
Rexburg Madison County Airport	4,858	May 15	Jun 3	Sep 23	129
Reynolds	3,930	May 21	Jun 12	Sep 28	126
Richfield	4,309	May 24	Jun 14	Sep 26	123
Rigby	4,856	May 9	May 25	Oct 5	148
Riggins	2,056	May 6	May 26	Oct 9	155
Saint Anthony	4,910	May 17	Jun 10	Sep 22	126
Saint Maries	2,151	May 3	May 18	Oct 4	152
Salmon-ksra	3,953	May 17	Jun 9	Sep 24	127
Sandpoint Experiment Station	2,126	May 8	May 25	Sep 28	141
Shoshone 1 WNW	3,950	Apr 24	May 12	Oct 16	173
Shoup	3,400	May 3	May 21	Oct 8	157
Silver City 5 W	6,160	May 31	Jun 17	Oct 6	128
Small 6N	5,740	Jun 5	Jun 21	Sep 20	106
Soda Springs Airport	5,842	Any month	Any month	Any month	69
Stanley	6,249	Any month	Any month	Any month	13
Stanley Ranger Station	6,495	Any month	Any month	Any month	29
Sugar City	4,925	May 29	Jun 18	Sep 13	106
Swan Falls Ph	2,325	Apr 12	May 6	Oct 26	193
Swan Valley	5,397	Any month	Any month	Any month	69
Taylor Rch	3,835	May 11	Jun 1	Sep 30	140
Tetonia Experiment Station	6,170	Jun 15	Jun 29	Sep 7	85
Twin Falls 6 E	3,960	May 6	May 26	Oct 3	150
Twin Falls Sun Valley Regional Airport	4,151	May 9	May 28	Oct 4	147
Twin Falls-kmvt	3,670	Apr 30	May 14	Oct 9	161
Wallace	2,710	May 5	May 21	Oct 2	149
Warren	5,907	Any month	Any month	Any month	23
Weiser	2,120	Apr 23	May 10	Oct 13	174
Winchester	3,972	May 23	Jun 19	Sep 25	121
Yellowpine	5,050	Jun 12	Jul 5	Sep 11	88
Yellowpine Bar	2,480	May 2	May 14	Oct 10	159

Frequently asked questions

When is the last frost in Idaho?

The median last spring frost (32°F) across Idaho's NOAA weather stations is May 16, based on 1991–2020 climate normals. It ranges from April 2 at Brownlee Dam to June 22 at McCall. For a safer planting date, use the 10%-risk date; the state median for that is June 4.

When is the first frost in Idaho?

The median first fall frost across Idaho's stations is September 29. The earliest median first frost is September 2 at McCall, and the latest is November 5 at Brownlee Dam.

How long is the growing season in Idaho?

The median frost-free season is 132 days across Idaho's stations, from 72 days at McCall to 216 days at Brownlee Dam.

When should I plant tomatoes in Idaho?

Plant tomatoes outdoors after your local last frost, ideally after the 10%-risk date when nights stay above 50°F. At a typical Idaho station that means starting seeds indoors 6–8 weeks before May 16 and transplanting from about June 4. Check your ZIP code, because dates vary by weeks across the state.

Can it frost in summer in Idaho?

Yes, at 17 stations in Idaho 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.