Idaho frost dates
The typical last spring frost ranges from Apr 24 in Boise to May 13 in Sun Valley.
4 of the 4 Idaho cities listed have typical frost dates. The longest frost-free season is 179 days in Boise; the shortest is 139 days in Sun Valley. For a single address, look up your ZIP code: rural ZIPs use their nearest suitable station.
| City | Last spring frost | 1 in 10 after | First fall frost | 1 in 10 before | Hard freeze (28°F) | Season |
|---|---|---|---|---|---|---|
| Boise | Apr 24 | May 9 | Oct 21 | Oct 5 | Apr 2 / Oct 31 | 179 days |
| Meridian | Apr 24 | May 9 | Oct 21 | Oct 5 | Apr 2 / Oct 31 | 179 days |
| Nampa | Apr 29 | May 18 | Oct 13 | Sep 29 | Apr 11 / Oct 25 | 164 days |
| Sun Valley | May 13 | Jun 3 | Oct 2 | Sep 15 | Apr 28 / Oct 14 | 139 days |
Reading the table: Nampa
In Nampa, the last spring frost typically comes around Apr 29: in half of years it is earlier, in half later. In 1 year in 10 it comes after May 18, 19 days later, so tender plants set out after that date have a 90% chance of escaping frost. In fall, the first frost typically arrives around Oct 13, and in 1 year in 10 before Sep 29. Hard freezes (28°F) usually end earlier in spring and start later in fall: around Apr 11 and Oct 25 in Nampa.
Frost dates at more Idaho weather stations
NOAA stations across Idaho used by our ZIP code lookup, named for the town they are in.
| Station | Elevation | Last spring frost | First fall frost |
|---|---|---|---|
| Aberdeen Exp Stn | 4,405 ft | May 21 (1 in 10 after Jun 13) | Sep 20 (before Sep 2) |
| Arco 17 Sw | 5,920 ft | May 24 (1 in 10 after Jun 15) | Oct 1 (before Sep 16) |
| Ashton 1N | 5,212 ft | May 21 (1 in 10 after Jun 13) | Sep 21 (before Sep 4) |
| Bayview Model Basin | 2,087 ft | May 22 (1 in 10 after Jun 6) | Sep 22 (before Sep 3) |
| Bern | 5,964 ft | Jun 17 (1 in 10 after Jul 4) | Sep 3 (before Aug 18) |
| Blackfoot Fire Dept | 4,499 ft | May 5 (1 in 10 after May 22) | Oct 3 (before Sep 16) |
| Boise 7 N | 3,885 ft | May 17 (1 in 10 after Jun 10) | Oct 12 (before Sep 27) |
| Bonners Ferry | 2,075 ft | Apr 30 (1 in 10 after May 16) | Oct 4 (before Sep 18) |
| Bruneau | 2,530 ft | Apr 17 (1 in 10 after May 7) | Oct 17 (before Oct 1) |
| Burley Muni Airport | 4,142 ft | May 7 (1 in 10 after May 23) | Oct 4 (before Sep 21) |
| Cabinet Gorge | 2,173 ft | May 9 (1 in 10 after May 25) | Oct 8 (before Sep 25) |
| Cambridge | 2,650 ft | May 15 (1 in 10 after Jun 4) | Sep 27 (before Sep 12) |
| Castleford 2 N | 3,825 ft | May 17 (1 in 10 after Jun 5) | Sep 29 (before Sep 11) |
| Coeur D'alene | 2,133 ft | Apr 22 (1 in 10 after May 6) | Oct 18 (before Oct 4) |
| Cottonwood 2 Wsw | 3,945 ft | May 6 (1 in 10 after May 26) | Oct 13 (before Sep 28) |
| Dubois Exp Stn | 5,450 ft | May 18 (1 in 10 after Jun 9) | Sep 30 (before Sep 14) |
| Elk Rvr | 2,866 ft | May 16 (1 in 10 after Jun 1) | Sep 23 (before Sep 6) |
| Emmett 2 E | 2,390 ft | Apr 30 (1 in 10 after May 17) | Oct 17 (before Oct 2) |
| Gibbonsville #2 | 4,480 ft | Jun 1 (1 in 10 after Jun 19) | Sep 17 (before Sep 2) |
| Grace | 5,550 ft | May 29 (1 in 10 after Jun 16) | Sep 17 (before Sep 1) |
| Grangeville | 3,300 ft | May 9 (1 in 10 after May 27) | Oct 3 (before Sep 14) |
| Hagerman 2 Sw | 2,897 ft | May 3 (1 in 10 after May 17) | Oct 1 (before Sep 16) |
| Hamer 4 Nw | 4,790 ft | Jun 3 (1 in 10 after Jun 21) | Sep 11 (before Aug 30) |
| Hazelton | 4,060 ft | May 7 (1 in 10 after May 26) | Oct 5 (before Sep 19) |
| Hill City 1 W | 5,100 ft | Jun 16 (1 in 10 after Jul 3) | Sep 6 (before Aug 20) |
| Homedale 1 Se | 2,230 ft | Apr 24 (1 in 10 after May 5) | Oct 9 (before Sep 26) |
| Idaho City | 3,965 ft | Jun 17 (1 in 10 after Jul 4) | Sep 5 (before Aug 23) |
| Idaho Falls - Kifi | 4,742 ft | May 9 (1 in 10 after Jun 2) | Oct 1 (before Sep 17) |
| Idaho Falls 16 Se | 5,828 ft | Jun 9 (1 in 10 after Jun 26) | Sep 11 (before Aug 27) |
| Idaho Falls 46 W | 4,938 ft | Jun 11 (1 in 10 after Jul 1) | Sep 6 (before Aug 24) |
| Idaho Falls Fanning Fld | 4,729 ft | May 23 (1 in 10 after Jun 13) | Sep 20 (before Sep 1) |
| Kellogg | 2,377 ft | May 14 (1 in 10 after Jun 3) | Sep 26 (before Sep 9) |
| Lewiston Nez Perce Co Airport | 1,436 ft | Apr 6 (1 in 10 after Apr 26) | Oct 26 (before Oct 10) |
| Lifton Pumping Stn | 5,935 ft | May 19 (1 in 10 after Jun 5) | Sep 21 (before Sep 5) |
| Malta | 4,521 ft | Jun 5 (1 in 10 after Jun 23) | Sep 13 (before Aug 28) |
| Malta 4 Ese | 4,590 ft | Jun 1 (1 in 10 after Jun 19) | Sep 19 (before Sep 2) |
| May 2SSE | 5,050 ft | Jun 12 (1 in 10 after Jun 29) | Sep 6 (before Aug 23) |
| Mccammon | 4,770 ft | May 23 (1 in 10 after Jun 10) | Sep 24 (before Sep 7) |
| Mtn Home | 3,140 ft | May 2 (1 in 10 after May 23) | Oct 8 (before Sep 25) |
| Mullan | 3,201 ft | May 12 (1 in 10 after Jun 19) | Sep 30 (before Sep 12) |
| Mullan Pass Vor/Dme | 6,028 ft | Jun 10 (1 in 10 after Jun 25) | Sep 23 (before Sep 4) |
| Nezperce | 3,248 ft | May 24 (1 in 10 after Jun 19) | Sep 20 (before Sep 1) |
| Ola | 3,075 ft | May 31 (1 in 10 after Jun 19) | Sep 16 (before Sep 2) |
| Parma Exp Stn | 2,290 ft | Apr 27 (1 in 10 after May 9) | Oct 9 (before Sep 26) |
| Payette | 2,150 ft | Apr 19 (1 in 10 after May 5) | Oct 20 (before Oct 6) |
| Picabo | 4,839 ft | Jun 16 (1 in 10 after Jun 30) | Sep 9 (before Aug 25) |
| Pierce | 3,080 ft | Jun 3 (1 in 10 after Jun 29) | Sep 7 (before Aug 22) |
| Plummer 3 Wsw | 2,905 ft | May 11 (1 in 10 after Jun 4) | Oct 5 (before Sep 15) |
| Pocatello 2 Ne | 4,832 ft | May 16 (1 in 10 after Jun 6) | Oct 2 (before Sep 14) |
| Potlatch 3 Nne | 2,760 ft | May 15 (1 in 10 after Jun 2) | Sep 21 (before Aug 31) |
| Preston | 4,719 ft | May 16 (1 in 10 after Jun 4) | Sep 28 (before Sep 14) |
| Priest Rvr Exp Stn | 2,371 ft | May 20 (1 in 10 after Jun 4) | Sep 13 (before Sep 1) |
| Rexburg Madison Co Airport | 4,858 ft | May 15 (1 in 10 after Jun 3) | Sep 23 (before Sep 8) |
| Saint Anthony | 4,910 ft | May 17 (1 in 10 after Jun 10) | Sep 22 (before Sep 5) |
| Saint Maries | 2,151 ft | May 3 (1 in 10 after May 18) | Oct 4 (before Sep 18) |
| Sandpoint Exp Stn | 2,126 ft | May 8 (1 in 10 after May 25) | Sep 28 (before Sep 11) |
| Shoshone 1 Wnw | 3,950 ft | Apr 24 (1 in 10 after May 12) | Oct 16 (before Oct 2) |
| Tetonia Exp Stn | 6,170 ft | Jun 15 (1 in 10 after Jun 29) | Sep 7 (before Aug 24) |
| Twin Falls Sun Vly Rgnl Airport | 4,151 ft | May 9 (1 in 10 after May 28) | Oct 4 (before Sep 20) |
| Winchester | 3,972 ft | May 23 (1 in 10 after Jun 19) | Sep 25 (before Sep 7) |
32°F dates from NOAA 1991-2020 freeze probabilities for each city's station. "1 in 10 after": a 10% chance of a later spring frost (planting is 90% safe after it). How to read frost dates.