Idaho frost dates
Across 127 weather stations in Idaho, the median last spring frost runs from Apr 2 in Brownlee Dam to Jun 22 in McCall, and the first fall frost from Sep 2 to Nov 5.
Idaho at a glance
- Weather stations
- 127
- Earliest last frost
- Apr 2 Brownlee Dam
- Latest last frost
- Jun 22 McCall
- Longest season
- 216 days Brownlee Dam
- Typical season
- about 132 frost-free days
- Hardiness zones
- Zones 4b to 7b
Frost dates by weather station
| Weather station | Last spring frost | First fall frost | Frost-free days | Zone |
|---|---|---|---|---|
| Aberdeen Experiment Station | May 21 | Sep 20 | 118 | 5b |
| American Falls | May 4 | Oct 8 | 155 | 6a |
| American Falls 6 mi NE | May 14 | Oct 2 | 138 | 5b |
| Arco | May 22 | Sep 22 | 119 | 5a |
| Arco 17 mi SW | May 24 | Oct 1 | 130 | 5a |
| Arrowrock Dam | Apr 28 | Oct 14 | 169 | 7a |
| Ashton | May 21 | Sep 21 | 121 | 5a |
| Bayview Model Basin | May 22 | Sep 22 | 122 | 6b |
| Bellevue | May 13 | Oct 2 | 139 | 6a |
| Bern | Jun 17 | Sep 3 | 77 | 5a |
| Blackfoot Fire Department | May 5 | Oct 3 | 149 | 5b |
| Boise | May 17 | Oct 12 | 147 | 7a |
| Boise Air Terminal | Apr 24 | Oct 21 | 179 | 7a |
| Boise Lucky Peak Dam | Apr 30 | Oct 22 | 173 | 7a |
| Bonners Ferry | Apr 30 | Oct 4 | 154 | 6b |
| Brownlee Dam | Apr 2 | Nov 5 | 216 | 7a |
| Bruneau | Apr 17 | Oct 17 | 181 | 7a |
| Buhl | Apr 25 | Oct 15 | 172 | 7a |
| Burley Municipal Airport | May 7 | Oct 4 | 150 | 6b |
| Cabinet Gorge | May 9 | Oct 8 | 153 | 6b |
| Cambridge | May 15 | Sep 27 | 134 | 6a |
| Cascade | May 30 | Sep 19 | 110 | 5a |
| Castleford | May 17 | Sep 29 | 132 | 7a |
| Challis Airport | May 14 | Sep 25 | 131 | 5b |
| Chilly Barton Flat | Jun 14 | Sep 8 | 86 | 5a |
| Coeur D'alene | Apr 22 | Oct 18 | 179 | 6b |
| Cottonwood | May 6 | Oct 13 | 156 | 6a |
| Council | May 10 | Oct 2 | 145 | 6a |
| Craters of the Moon | Jun 19 | Sep 9 | 81 | 5a |
| Deer Flat Dam | Apr 23 | Oct 18 | 178 | 7a |
| Downey | May 31 | Sep 18 | 110 | 6b |
| Driggs | Jun 13 | Sep 9 | 86 | 5a |
| Dubois Experiment Station | May 18 | Sep 30 | 132 | 5b |
| Dworshak Fish Hatchery | Apr 20 | Oct 20 | 182 | 7a |
| Elk River | May 16 | Sep 23 | 128 | 6b |
| Emmett | Apr 30 | Oct 17 | 168 | 7a |
| Fairfield Ranger Station | Jun 8 | Sep 14 | 97 | 5a |
| Fenn Ranger Station | Apr 26 | Oct 20 | 176 | 7a |
| Fort Hall | May 20 | Sep 20 | 119 | 5b |
| Garden Valley | Jun 1 | Sep 10 | 102 | 6b |
| Gibbonsville | Jun 1 | Sep 17 | 107 | 5b |
| Glenns Ferry | May 1 | Oct 3 | 154 | 7a |
| Grace | May 29 | Sep 17 | 111 | 5b |
| Grand View | Apr 28 | Oct 6 | 162 | 7a |
| Grangeville | May 9 | Oct 3 | 146 | 6b |
| Hagerman | May 3 | Oct 1 | 151 | 7a |
| Hamer | Jun 3 | Sep 11 | 98 | 5a |
| Hazelton | May 7 | Oct 5 | 149 | 6b |
| Hill City | Jun 16 | Sep 6 | 80 | 5a |
| Homedale | Apr 24 | Oct 9 | 169 | 7a |
| Howe | May 24 | Sep 14 | 113 | 5a |
| Idaho City | Jun 17 | Sep 5 | 80 | 6b |
| Idaho Falls - Kifi | May 9 | Oct 1 | 142 | 5b |
| Idaho Falls 16 mi SE | Jun 9 | Sep 11 | 93 | 5b |
| Idaho Falls 46 mi W | Jun 11 | Sep 6 | 89 | 5a |
| Idaho Falls Fanning Field | May 23 | Sep 20 | 114 | 5b |
| Jerome | May 2 | Oct 14 | 166 | 6b |
| Jerome County Airport | May 1 | Oct 14 | 165 | 6b |
| Kamiah | Apr 29 | Oct 5 | 163 | 7a |
| Kellogg | May 14 | Sep 26 | 131 | 6b |
| Kooskia | Apr 30 | Oct 11 | 162 | 7a |
| Lava Hot Springs | May 21 | Sep 21 | 118 | 6b |
| Lewiston Nez Perce County Airport | Apr 6 | Oct 26 | 200 | 7b |
| Lifton Pumping Station | May 19 | Sep 21 | 123 | 5a |
| Lowell Three Rivers | Apr 16 | Oct 25 | 191 | 7a |
| Lowman | Jun 6 | Sep 4 | 87 | 6b |
| Mackay Lost River Ranger Station | Jun 1 | Sep 20 | 109 | 5a |
| Malad City | May 22 | Sep 20 | 116 | 6a |
| Malta | Jun 5 | Sep 13 | 96 | 6b |
| Malta 4 mi ESE | Jun 1 | Sep 19 | 111 | 6a |
| Massacre Rocks State Park | May 20 | Sep 26 | 125 | 6a |
| May | Jun 12 | Sep 6 | 85 | 5a |
| McCall | Jun 22 | Sep 2 | 72 | 5a |
| McCall Airport | Jun 10 | Sep 10 | 93 | 5a |
| McCammon | May 23 | Sep 24 | 121 | 5b |
| Middle Fork Lodge | May 21 | Sep 18 | 115 | 5a |
| Minidoka Dam | May 16 | Oct 1 | 136 | 6a |
| Monteview | Jun 12 | Sep 7 | 87 | 4b |
| Mountain Home | May 2 | Oct 8 | 157 | 7a |
| Mullan | May 12 | Sep 30 | 138 | 6a |
| Mullan Pass Vor/Dme | Jun 10 | Sep 23 | 104 | 6a |
| Murphy | May 17 | Sep 30 | 134 | 7a |
| Nampa Sugar Factory | Apr 29 | Oct 13 | 164 | 7a |
| Nezperce | May 24 | Sep 20 | 116 | 6b |
| Oakley | May 15 | Oct 2 | 137 | 6b |
| Ola | May 31 | Sep 16 | 108 | 7a |
| Parma Experiment Station | Apr 27 | Oct 9 | 165 | 7a |
| Paul | May 6 | Oct 6 | 151 | 6a |
| Payette | Apr 19 | Oct 20 | 183 | 7a |
| Picabo | Jun 16 | Sep 9 | 85 | 6a |
| Pierce | Jun 3 | Sep 7 | 93 | 6a |
| Plummer | May 11 | Oct 5 | 143 | 6b |
| Pocatello | May 16 | Oct 2 | 137 | 6b |
| Pocatello City | May 2 | Oct 11 | 161 | 6a |
| Pocatello Regional Airport | May 23 | Sep 18 | 117 | 6a |
| Porthill | May 4 | Sep 30 | 145 | 6a |
| Potlatch | May 15 | Sep 21 | 126 | 6b |
| Powell | May 31 | Sep 12 | 102 | 5b |
| Preston | May 16 | Sep 28 | 133 | 6a |
| Prichard | May 31 | Sep 5 | 95 | 6a |
| Priest River Experiment Station | May 20 | Sep 13 | 114 | 6a |
| Rexburg BYU Idaho | May 12 | Sep 24 | 132 | 5a |
| Rexburg Madison County Airport | May 15 | Sep 23 | 129 | 5a |
| Reynolds | May 21 | Sep 28 | 126 | 7a |
| Richfield | May 24 | Sep 26 | 123 | 6a |
| Rigby | May 9 | Oct 5 | 148 | 5b |
| Riggins | May 6 | Oct 9 | 155 | 6b |
| Saint Anthony | May 17 | Sep 22 | 126 | 5a |
| Saint Maries | May 3 | Oct 4 | 152 | 6b |
| Salmon-Ksra | May 17 | Sep 24 | 127 | 5b |
| Sandpoint Experiment Station | May 8 | Sep 28 | 141 | 6b |
| Shoshone | Apr 24 | Oct 16 | 173 | 6a |
| Shoup | May 3 | Oct 8 | 157 | 6a |
| Silver City | May 31 | Oct 6 | 128 | 7a |
| Small | Jun 5 | Sep 20 | 106 | 5b |
| Sugar City | May 29 | Sep 13 | 106 | 5a |
| Swan Falls Powerhouse | Apr 12 | Oct 26 | 193 | 7a |
| Taylor Ranch | May 11 | Sep 30 | 140 | 5a |
| Tetonia Experiment Station | Jun 15 | Sep 7 | 85 | 5a |
| Twin Falls | May 6 | Oct 3 | 150 | 6b |
| Twin Falls Sun Valley Regional Airport | May 9 | Oct 4 | 147 | 6b |
| Twin Falls-Kmvt | Apr 30 | Oct 9 | 161 | 7a |
| Wallace | May 5 | Oct 2 | 149 | 6b |
| Weiser | Apr 23 | Oct 13 | 174 | 7a |
| Winchester | May 23 | Sep 25 | 121 | 6b |
| Yellowpine | Jun 12 | Sep 11 | 88 | 5a |
| Yellowpine Bar | May 2 | Oct 10 | 159 | 5b |
Median dates from NOAA 1991–2020 climate normals. How to read them.