Frost dates 2026–2027

Idaho frost dates by city

Across 36 Idaho cities, the average first fall frost ranges from September 20 in Shelley to October 26 in Lewiston. Median 32°F dates from NOAA 1991–2020 normals.

CityPopulationLast spring frostFirst fall frostGrowing seasonZone
Boise 238,429 Apr 24 Oct 21 179 days 7a
Meridian 142,988 Apr 24 Oct 21 179 days 7a
Nampa 120,384 Apr 29 Oct 13 164 days 7a
Caldwell 76,629 Apr 29 Oct 13 164 days 7a
Idaho Falls 71,785 May 9 Oct 1 142 days 5b
Pocatello 58,771 May 2 Oct 11 161 days 6a
Coeur d'Alene 58,179 Apr 22 Oct 18 179 days 6b
Twin Falls 56,216 Apr 30 Oct 9 161 days 7a
Post Falls 46,715 Apr 22 Oct 18 179 days 6b
Rexburg 40,334 May 12 Sep 24 132 days 5a
Lewiston 34,717 Apr 6 Oct 26 200 days 7a
Eagle 34,658 Apr 29 Oct 13 164 days 7a
Kuna 31,525 Apr 24 Oct 21 179 days 7a
Moscow 26,721 Apr 29 Oct 2 159 days 6b
Star 20,874 Apr 29 Oct 13 164 days 7a
Ammon 20,119 May 9 Oct 1 142 days 5b
Hayden 17,363 Apr 22 Oct 18 179 days 6b
Chubbuck 16,823 May 16 Oct 2 137 days 6b
Mountain Home 16,779 May 2 Oct 8 157 days 7a
Jerome 13,731 May 2 Oct 14 166 days 6b
Blackfoot 13,361 May 5 Oct 3 149 days 5b
Rathdrum 13,227 Apr 22 Oct 18 179 days 6b
Garden City 13,047 May 17 Oct 12 147 days 7a
Middleton 12,600 Apr 29 Oct 13 164 days 7a
Burley 12,409 May 7 Oct 4 150 days 6b
Sandpoint 10,645 May 8 Sep 28 141 days 6b
Hailey 10,053 May 13 Oct 2 139 days 6a
Emmett 8,900 Apr 30 Oct 17 168 days 7a
Payette 8,813 Apr 19 Oct 20 183 days 7a
Fruitland 7,213 Apr 22 Oct 9 168 days 7a
Rupert 6,460 May 6 Oct 6 151 days 6a
Weiser 6,249 Apr 23 Oct 13 174 days 7a
Preston 6,177 May 16 Sep 28 133 days 6a
Kimberly 5,798 May 6 Oct 3 150 days 6b
Rigby 5,757 May 9 Oct 5 148 days 5b
Shelley 5,303 May 23 Sep 20 114 days 5b
Cities with 5,000+ residents (Census 2025 estimates). Sources: NOAA NCEI 1991–2020 normals; USDA/Oregon State PRISM 2023 hardiness zones.

Growing zones in Idaho · Frost dates in other states