Frost Dates for Nampa, ID
In Nampa, ID, the average last spring frost is around Apr 29 and the average first fall frost around Oct 13, for a growing season of about 164 days. For frost-tender plants, wait until May 18, when the chance of frost drops to 10%.
Based on NOAA 1991–2020 records from the Nampa Sugar Factory, ID weather station, 1 mile away, elevation 2,470 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 18 | Sep 29 |
| 20% | May 9 | Oct 3 |
| 30% | May 5 | Oct 6 |
| 40% | May 1 | Oct 9 |
| 50% | Apr 29 | Oct 13 |
| 60% | Apr 27 | Oct 16 |
| 70% | Apr 23 | Oct 19 |
| 80% | Apr 20 | Oct 22 |
| 90% | Apr 15 | Oct 28 |
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 16 | Sep 30 |
| Frost / freeze (32°F) | Apr 29 | Oct 13 |
| Hard freeze (28°F) | Apr 11 | Oct 25 |
Planting calendar for Nampa
Transplant May 6 – May 20
Transplant May 13 – May 27
Transplant May 13 – May 27
Transplant May 6 – May 20
Sow or transplant May 6 – May 20
Sow or transplant May 6 – May 20
Sow or transplant May 13 – May 27
Sow or transplant Apr 1 – Apr 15
Fall sowing Aug 18 – Sep 15
Fall sowing Aug 18 – Sep 8
Fall sowing Aug 4 – Aug 18
Sow or transplant Apr 1 – Apr 15
Fall sowing Aug 4 – Sep 1
Transplant Apr 15 – Apr 29
Fall sowing Jul 21 – Aug 4
Transplant Apr 8 – Apr 22
Fall sowing Jul 21 – Aug 4
Fall sowing Jul 21 – Aug 4
Fall sowing Sep 1 – Sep 22
Fall sowing Aug 4 – Aug 18
Plant Apr 1 – Apr 15
Based on the average last frost (Apr 29) and first frost (Oct 13). The dashed lines mark those dates. Seed packets list days to maturity; adjust for your varieties.