Frost dates in Idaho
Across Idaho's 127 NOAA stations with a frost every year, the typical last spring frost ranges from April 2 at Brownlee Dam (1,840 feet above sea level) to June 22 at Mccall (5,030 feet above sea level). The middle station's date is May 16.
Look up your ZIP code
Last frost across Idaho
The frost-free season runs from 72 days at Mccall to 216 days at Brownlee Dam.
The station with the latest frost sits about 3,200 feet higher than the one with the earliest.
At 17 stations, all high or far north, frost is possible in every month.
These are typical dates: in half of springs the last frost comes later. Each place's page, and each ZIP code lookup, also gives the late-year date, after which only 1 spring in 10 has a frost. That's the safer date for tender plants.
Frost dates for Idaho's larger places
| Place | Last spring frost | First fall frost | Season | Zone |
|---|---|---|---|---|
| Boise | April 24 | October 21 | 179 days | 7a |
| Idaho Falls | May 23 | September 20 | 114 days | 5b |
| Nampa | April 29 | October 13 | 164 days | 7a |
Typical (1-in-2) dates. Each place's page has the early and late years, a planting calendar and a printable planner. Zones are for the ZIP code nearest each place's center.
Hardiness zones in Idaho
Idaho's 313 ZIP codes in the USDA list fall in zones 4a to 7b: 4a (1 percent), 4b (1 percent), 5a (13 percent), 5b (14 percent), 6a (17 percent), 6b (28 percent), 7a (26 percent) and 7b (1 percent). Compared with the 2012 map, 51 percent of them moved to a warmer half zone (16 by a full zone or more), 47 percent stayed the same and 7 moved to a colder one.
A hardiness zone is about the coldest night of winter, which decides which shrubs, trees and perennials survive. Frost dates are about spring and fall, which decide when to plant. You need both. Read more about what the zones mean and what changed in 2023.
Every NOAA station in Idaho
All 144 stations in Idaho with frost statistics in NOAA's 1991 to 2020 normals, from A to Z. Station names are usually a town, an airport, or a distance and direction from a town. Find one near you and at a similar elevation.
| Station | Elevation (feet) | Last spring frost | First fall frost | Season (days) |
|---|---|---|---|---|
| Aberdeen Exp Station | 4,410 | May 21 | September 20 | 118 |
| American Falls | 4,510 | May 4 | October 8 | 155 |
| American Falls 6 NE | 4,420 | May 14 | October 2 | 138 |
| Arco | 5,320 | May 22 | September 22 | 119 |
| Arco 17 SW | 5,920 | May 24 | October 1 | 130 |
| Arrowrock Dam | 3,230 | April 28 | October 14 | 169 |
| Ashton 1 N | 5,210 | May 21 | September 21 | 121 |
| Bayview Model Basin | 2,090 | May 22 | September 22 | 122 |
| Bellevue | 5,190 | May 13 | October 2 | 139 |
| Bern | 5,960 | June 17 | September 3 | 77 |
| Blackfoot Fire Dept | 4,500 | May 5 | October 3 | 149 |
| Boise 7 N | 3,880 | May 17 | October 12 | 147 |
| Boise Air Terminal | 2,810 | April 24 | October 21 | 179 |
| Boise Lucky Peak Dam | 2,840 | April 30 | October 22 | 173 |
| Bonners Ferry | 2,080 | April 30 | October 4 | 154 |
| Brownlee Dam | 1,840 | April 2 | November 5 | 216 |
| Bruneau | 2,530 | April 17 | October 17 | 181 |
| Buhl #2 | 3,800 | April 25 | October 15 | 172 |
| Burley Municipal Airport | 4,140 | May 7 | October 4 | 150 |
| Cabinet Gorge | 2,170 | May 9 | October 8 | 153 |
| Cambridge | 2,650 | May 15 | September 27 | 134 |
| Cascade 1 NW | 4,900 | May 30 | September 19 | 110 |
| Castleford 2 N | 3,830 | May 17 | September 29 | 132 |
| Challis Airport | 5,030 | May 14 | September 25 | 131 |
| Chilly Barton Flat | 6,260 | June 14 | September 8 | 86 |
| Coeur D'alene | 2,130 | April 22 | October 18 | 179 |
| Cottonwood 2 WSW | 3,940 | May 6 | October 13 | 156 |
| Council | 2,940 | May 10 | October 2 | 145 |
| Craters of the Moon | 5,920 | June 19 | September 9 | 81 |
| Deadwood Lodge | 5,950 | Frost possible any month | 32 | |
| Deer Flat Dam | 2,510 | April 23 | October 18 | 178 |
| Dixie | 5,620 | Frost possible any month | 29 | |
| Dixie N | 5,740 | Frost possible any month | 30 | |
| Downey | 4,870 | May 31 | September 18 | 110 |
| Driggs | 6,120 | June 13 | September 9 | 86 |
| Dubois Exp Station | 5,450 | May 18 | September 30 | 132 |
| Dworshak Fish Hatchery | 990 | April 20 | October 20 | 182 |
| Elk City 1 NE | 4,060 | Frost possible any month | 64 | |
| Elk River | 2,870 | May 16 | September 23 | 128 |
| Emmett 2 E | 2,390 | April 30 | October 17 | 168 |
| Fairfield RS | 5,070 | June 8 | September 14 | 97 |
| Fenn RS | 1,560 | April 26 | October 20 | 176 |
| Fort Hall 1 NNE | 4,470 | May 20 | September 20 | 119 |
| Garden Valley | 3,100 | June 1 | September 10 | 102 |
| Gibbonsville #2 | 4,480 | June 1 | September 17 | 107 |
| Glenns Ferry | 2,470 | May 1 | October 3 | 154 |
| Grace | 5,550 | May 29 | September 17 | 111 |
| Grand View 4 NW | 2,400 | April 28 | October 6 | 162 |
| Grangeville | 3,300 | May 9 | October 3 | 146 |
| Hagerman 2 SW | 2,900 | May 3 | October 1 | 151 |
| Hamer 4 NW | 4,790 | June 3 | September 11 | 98 |
| Hazelton | 4,060 | May 7 | October 5 | 149 |
| Headquarters | 3,200 | Frost possible any month | 81 | |
| Hill City 1 W | 5,100 | June 16 | September 6 | 80 |
| Homedale 1 SE | 2,230 | April 24 | October 9 | 169 |
| Howe | 4,820 | May 24 | September 14 | 113 |
| Idaho City | 3,970 | June 17 | September 5 | 80 |
| Idaho Falls - Kifi | 4,740 | May 9 | October 1 | 142 |
| Idaho Falls 16 SE | 5,830 | June 9 | September 11 | 93 |
| Idaho Falls 46 W | 4,940 | June 11 | September 6 | 89 |
| Idaho Falls Fanning Field | 4,730 | May 23 | September 20 | 114 |
| Island Park | 6,290 | Frost possible any month | 49 | |
| Jerome | 3,740 | May 2 | October 14 | 166 |
| Jerome Co Airport | 4,050 | May 1 | October 14 | 165 |
| Kamiah | 1,210 | April 29 | October 5 | 163 |
| Kellogg | 2,380 | May 14 | September 26 | 131 |
| Ketchum RS | 5,890 | Frost possible any month | 77 | |
| Kooskia 5 SSE | 2,330 | April 30 | October 11 | 162 |
| Lava Hot Springs | 4,600 | May 21 | September 21 | 118 |
| Leadore #2 | 6,000 | Frost possible any month | 50 | |
| Lewiston Nez Perce Co Airport | 1,440 | April 6 | October 26 | 200 |
| Lifton Pumping Station | 5,940 | May 19 | September 21 | 123 |
| Lowell Three Rivers | 1,480 | April 16 | October 25 | 191 |
| Lowman | 3,920 | June 6 | September 4 | 87 |
| Mackay Lost River RS | 5,900 | June 1 | September 20 | 109 |
| Malad City | 4,470 | May 22 | September 20 | 116 |
| Malta | 4,520 | June 5 | September 13 | 96 |
| Malta 4 ESE | 4,590 | June 1 | September 19 | 111 |
| Massacre Rocks SP | 4,200 | May 20 | September 26 | 125 |
| May 2 SSE | 5,050 | June 12 | September 6 | 85 |
| Mccall | 5,030 | June 22 | September 2 | 72 |
| Mccall Airport | 5,010 | June 10 | September 10 | 93 |
| Mccammon | 4,770 | May 23 | September 24 | 121 |
| Middle Fork Lodge | 4,480 | May 21 | September 18 | 115 |
| Minidoka Dam | 4,160 | May 16 | October 1 | 136 |
| Monteview | 4,820 | June 12 | September 7 | 87 |
| Moscow U of I | 2,660 | Frost possible any month | 85 | |
| Mountain Home | 3,140 | May 2 | October 8 | 157 |
| Mullan | 3,200 | May 12 | September 30 | 138 |
| Mullan Pass Vor/dme | 6,030 | June 10 | September 23 | 104 |
| Murphy (desert) Hot Springs | 5,150 | Frost possible any month | 87 | |
| Murphy 10 W | 3,950 | May 17 | September 30 | 134 |
| Nampa Sugar Factory | 2,470 | April 29 | October 13 | 164 |
| New Meadows RS | 3,860 | Frost possible any month | 62 | |
| Nezperce | 3,250 | May 24 | September 20 | 116 |
| Oakley | 4,560 | May 15 | October 2 | 137 |
| Ola | 3,070 | May 31 | September 16 | 108 |
| Parma Exp Station | 2,290 | April 27 | October 9 | 165 |
| Paul 1 ENE | 4,150 | May 6 | October 6 | 151 |
| Payette | 2,150 | April 19 | October 20 | 183 |
| Picabo | 4,840 | June 16 | September 9 | 85 |
| Pierce | 3,080 | June 3 | September 7 | 93 |
| Plummer 3 WSW | 2,900 | May 11 | October 5 | 143 |
| Pocatello 2 NE | 4,830 | May 16 | October 2 | 137 |
| Pocatello City | 4,460 | May 2 | October 11 | 161 |
| Pocatello Regional Airport | 4,480 | May 23 | September 18 | 117 |
| Porthill 1 SW | 1,800 | May 4 | September 30 | 145 |
| Potlatch 3 NNE | 2,760 | May 15 | September 21 | 126 |
| Powell | 3,530 | May 31 | September 12 | 102 |
| Preston | 4,720 | May 16 | September 28 | 133 |
| Prichard 3 ESE | 2,550 | May 31 | September 5 | 95 |
| Priest River Exp Station | 2,370 | May 20 | September 13 | 114 |
| Red River RS | 4,350 | Frost possible any month | 59 | |
| Rexburg Byu Idaho | 5,010 | May 12 | September 24 | 132 |
| Rexburg Madison Co Airport | 4,860 | May 15 | September 23 | 129 |
| Reynolds | 3,930 | May 21 | September 28 | 126 |
| Richfield | 4,310 | May 24 | September 26 | 123 |
| Rigby | 4,860 | May 9 | October 5 | 148 |
| Riggins | 2,060 | May 6 | October 9 | 155 |
| Saint Anthony | 4,910 | May 17 | September 22 | 126 |
| Saint Maries | 2,150 | May 3 | October 4 | 152 |
| Salmon-Ksra | 3,950 | May 17 | September 24 | 127 |
| Sandpoint Exp Station | 2,130 | May 8 | September 28 | 141 |
| Shoshone 1 WNW | 3,950 | April 24 | October 16 | 173 |
| Shoup | 3,400 | May 3 | October 8 | 157 |
| Silver City 5 W | 6,160 | May 31 | October 6 | 128 |
| Small 6 N | 5,740 | June 5 | September 20 | 106 |
| Soda Springs Airport | 5,840 | Frost possible any month | 69 | |
| Stanley | 6,250 | Frost possible any month | 13 | |
| Stanley RS | 6,500 | Frost possible any month | 29 | |
| Sugar City | 4,920 | May 29 | September 13 | 106 |
| Swan Falls PH | 2,330 | April 12 | October 26 | 193 |
| Swan Valley | 5,400 | Frost possible any month | 69 | |
| Taylor Ranch | 3,840 | May 11 | September 30 | 140 |
| Tetonia Exp Station | 6,170 | June 15 | September 7 | 85 |
| Twin Falls 6 E | 3,960 | May 6 | October 3 | 150 |
| Twin Falls Sun Vly Regional Airport | 4,150 | May 9 | October 4 | 147 |
| Twin Falls-KMVT | 3,670 | April 30 | October 9 | 161 |
| Wallace | 2,710 | May 5 | October 2 | 149 |
| Warren | 5,910 | Frost possible any month | 23 | |
| Weiser | 2,120 | April 23 | October 13 | 174 |
| Winchester | 3,970 | May 23 | September 25 | 121 |
| Yellowpine | 5,050 | June 12 | September 11 | 88 |
| Yellowpine Bar | 2,480 | May 2 | October 10 | 159 |
Typical (1-in-2) dates at 32°F. For the early and late years, and a planting calendar built from your own dates, look up your ZIP code.