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Frost Dates and Planting Windows in Idaho

The 32°F frost dates at the 127 weather stations in Idaho with NOAA's 1991–2020 Climate Normals, and the planting windows they give. These are long-term statistics, not a forecast. For the dates at the station nearest you, enter your ZIP code.

The planner uses the weather station nearest your ZIP code.

Frost dates across Idaho

Each risk level uses a date with a set chance of frost. In spring, it's the chance of a 32°F frost on or after the last-frost date. In fall, it's the chance of the first 32°F frost on or before the first-frost date. At the Typical level (30%), the last frost ranges from April 9 to June 29 across the state, and the first frost from August 28 to October 31.

32°F frost dates: earliest and latest among 127 stations, by risk level
Risk levelEarliest last frostLatest last frostEarliest first frostLatest first frost
Conservative (10%)April 20BROWNLEE DAM, ID USJuly 10MCCALL, ID USAugust 14MCCALL, ID USOctober 24BROWNLEE DAM, ID US
Typical (30%)April 9BROWNLEE DAM, ID USJune 29MCCALL, ID USAugust 28MCCALL, ID USOctober 31BROWNLEE DAM, ID US
Aggressive (50%)April 2BROWNLEE DAM, ID USJune 22MCCALL, ID USSeptember 2MCCALL, ID USNovember 5BROWNLEE DAM, ID US

Growing season length

The growing season is the stretch between the last spring frost and the first fall frost at 32°F. NOAA gives it as a length with a chance of being at least that long. Each risk level uses the length with that chance of a shorter season, so Conservative shows the shortest lengths.

Growing season at 32°F: shortest and longest among 127 stations
Risk levelShortestLongest
Conservative (90% chance of at least this long)46 daysMCCALL, ID US193 daysBROWNLEE DAM, ID US
Typical (70% chance of at least this long)61 daysMCCALL, ID US206 daysBROWNLEE DAM, ID US
Aggressive (50% chance of at least this long)72 daysMCCALL, ID US216 daysBROWNLEE DAM, ID US
Number of stations by growing season length, Typical (70% chance of at least this long)
Growing seasonStations
60–79 days14
80–99 days17
100–119 days27
120–139 days26
140–159 days27
160–179 days12
180–199 days3
200–219 days1

Planting windows across Idaho

For each crop, the earliest start and the latest end of its Typical windows among the stations. A window at any one station is shorter and falls inside this span. Transplant dates are for seedlings. A fall window is left out at stations where it would start on or before the last day of the spring window, so some rows cover fewer stations.

Typical planting windows (30% frost dates): earliest start and latest end among stations
Crop and taskEarliest startLatest endStations
Basil: Transplant outdoorsApril 23July 13127 of 127
Bean: Sow outdoorsApril 9June 29127 of 127
Beet: Sow outdoorsMarch 12June 29127 of 127
Beet: Sow for fallJune 12September 11108 of 127
Broccoli: Transplant outdoorsMarch 12June 15127 of 127
Broccoli: Transplant for fallMay 28September 11111 of 127
Brussels sprouts: Transplant outdoorsMarch 12June 15127 of 127
Brussels sprouts: Transplant for fallMay 16September 2193 of 127
Cabbage: Transplant outdoorsMarch 12June 15127 of 127
Cabbage: Transplant for fallMay 28September 11107 of 127
Cantaloupe: Transplant outdoorsApril 23July 13127 of 127
Cantaloupe: Sow outdoorsApril 23July 13127 of 127
Carrot: Sow outdoorsMarch 12June 29127 of 127
Carrot: Sow for fallJune 5September 199 of 127
Cucumber: Transplant outdoorsApril 16July 6127 of 127
Cucumber: Sow outdoorsApril 9June 29127 of 127
Eggplant: Transplant outdoorsApril 23July 13127 of 127
Garlic: Plant for fallAugust 28November 14127 of 127
Lettuce: Transplant outdoorsMarch 12June 15127 of 127
Lettuce: Sow outdoorsMarch 12June 15127 of 127
Lettuce: Sow for fallMay 28September 21111 of 127
Onion: Transplant or plant setsMarch 12June 15127 of 127
Peas: Sow outdoorsMarch 12June 15127 of 127
Peas: Sow for fallJune 4September 11121 of 127
Pepper: Transplant outdoorsApril 23July 13127 of 127
Potato: Plant seed potatoesMarch 12June 29127 of 127
Pumpkin: Sow outdoorsApril 23July 13127 of 127
Radish: Sow outdoorsMarch 12June 15127 of 127
Radish: Sow for fallJuly 10October 11127 of 127
Spinach: Transplant outdoorsMarch 12June 15127 of 127
Spinach: Sow outdoorsMarch 12June 15127 of 127
Spinach: Sow for fallJune 16September 24126 of 127
Summer squash: Transplant outdoorsApril 16July 6127 of 127
Summer squash: Sow outdoorsApril 9June 29127 of 127
Sweet corn: Sow outdoorsApril 9June 29127 of 127
Sweet potato: Plant slipsApril 16July 13127 of 127
Tomato: Transplant outdoorsApril 23July 13127 of 127
Turnip: Sow outdoorsMarch 12June 15127 of 127
Turnip: Sow for fallJune 16September 21126 of 127
Watermelon: Transplant outdoorsApril 23July 13127 of 127
Watermelon: Sow outdoorsApril 23July 13127 of 127

Weather stations in Idaho

Every station in Idaho with NOAA frost-date normals, with its Typical 32°F frost dates and growing season. 17 of them have no 32°F frost dates.

Data sources

NOAA U.S. Climate Normals, frost dates, 1991–2020 normals, version 1.0.1
Files: us-climate-normals_1991-2020_v1.0.1_annualseasonal_multivariate_by-station_c20230404.tar.gz, inventory_30yr.txt from NOAA NCEI. Retrieved October 10, 2026.