Frost Dates for Idaho Falls, ID
In Idaho Falls, ID, the average last spring frost is around May 9 and the average first fall frost around Oct 1, for a growing season of about 142 days. For frost-tender plants, wait until Jun 2, when the chance of frost drops to 10%.
Based on NOAA 1991–2020 records from the Idaho Falls - Kifi, ID weather station, 2 miles away, elevation 4,742 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% | Jun 2 | Sep 17 |
| 20% | May 23 | Sep 21 |
| 30% | May 17 | Sep 25 |
| 40% | May 13 | Sep 28 |
| 50% | May 9 | Oct 1 |
| 60% | May 7 | Oct 3 |
| 70% | May 4 | Oct 6 |
| 80% | May 1 | Oct 10 |
| 90% | Apr 27 | Oct 15 |
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 30 | Sep 20 |
| Frost / freeze (32°F) | May 9 | Oct 1 |
| Hard freeze (28°F) | Apr 28 | Oct 13 |
Planting calendar for Idaho Falls
Transplant May 16 – May 30
Transplant May 23 – Jun 6
Transplant May 23 – Jun 6
Transplant May 16 – May 30
Sow or transplant May 16 – May 30
Sow or transplant May 16 – May 30
Sow or transplant May 23 – Jun 6
Sow or transplant Apr 11 – Apr 25
Fall sowing Aug 6 – Sep 3
Fall sowing Aug 6 – Aug 27
Fall sowing Jul 23 – Aug 6
Sow or transplant Apr 11 – Apr 25
Fall sowing Jul 23 – Aug 20
Transplant Apr 25 – May 9
Fall sowing Jul 9 – Jul 23
Transplant Apr 18 – May 2
Fall sowing Jul 9 – Jul 23
Fall sowing Jul 9 – Jul 23
Fall sowing Aug 20 – Sep 10
Fall sowing Jul 23 – Aug 6
Plant Apr 11 – Apr 25
Based on the average last frost (May 9) and first frost (Oct 1). The dashed lines mark those dates. Seed packets list days to maturity; adjust for your varieties.