Frost Dates for Boise City, ID
In Boise City, ID, the average last spring frost is around Apr 24 and the average first fall frost around Oct 21, for a growing season of about 179 days. For frost-tender plants, wait until May 9, when the chance of frost drops to 10%.
Based on NOAA 1991–2020 records from the Boise Air Terminal, ID weather station, 2 miles away, elevation 2,814 ft. Frost can come earlier in low spots and valleys and later near cities and large lakes.
Frost probability by date
Chance of a 32°F frost after the spring date, or before the fall date.
| Chance | Last spring frost | First fall frost |
|---|---|---|
| 10% | May 9 | Oct 5 |
| 20% | May 4 | Oct 10 |
| 30% | Apr 30 | Oct 14 |
| 40% | Apr 27 | Oct 18 |
| 50% | Apr 24 | Oct 21 |
| 60% | Apr 21 | Oct 24 |
| 70% | Apr 17 | Oct 27 |
| 80% | Apr 12 | Oct 31 |
| 90% | Apr 4 | Nov 5 |
Light frost vs. hard freeze
Average (50%) dates for each temperature. Tender plants are damaged at 36°F; most hardy crops survive until 28°F.
| Temperature | Last in spring | First in fall |
|---|---|---|
| Light frost (36°F) | May 8 | Oct 8 |
| Frost / freeze (32°F) | Apr 24 | Oct 21 |
| Hard freeze (28°F) | Apr 2 | Oct 31 |
Planting calendar for Boise City
Transplant May 1 – May 15
Transplant May 8 – May 22
Transplant May 8 – May 22
Transplant May 1 – May 15
Sow or transplant May 1 – May 15
Sow or transplant May 1 – May 15
Sow or transplant May 8 – May 22
Sow or transplant Mar 27 – Apr 10
Fall sowing Aug 26 – Sep 23
Fall sowing Aug 26 – Sep 16
Fall sowing Aug 12 – Aug 26
Sow or transplant Mar 27 – Apr 10
Fall sowing Aug 12 – Sep 9
Transplant Apr 10 – Apr 24
Fall sowing Jul 29 – Aug 12
Transplant Apr 3 – Apr 17
Fall sowing Jul 29 – Aug 12
Fall sowing Jul 29 – Aug 12
Fall sowing Sep 9 – Sep 30
Fall sowing Aug 12 – Aug 26
Plant Mar 27 – Apr 10
Based on the average last frost (Apr 24) and first frost (Oct 21). The dashed lines mark those dates. Seed packets list days to maturity; adjust for your varieties.