Frost dates for 83211American Falls, ID
The average last spring frost in American Falls is May 20 and the average first fall frost is September 26, giving a typical growing season of about 125 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 20
- Average first fall frost
- Sep 26
- Growing season
- 125 days
Safer after Jun 9 (1-in-10 risk)
Possible by Sep 8 (1-in-10 risk)
Last frost typically in 198 days
Frost risk by date
NOAA reports frost dates as probabilities. The middle date is the average (a 50% chance). For spring, the 10% date is a safer planting date: frost after it happens in about 1 year in 10. Light frost (36°F) can damage tender plants; a hard freeze (28°F) kills most annuals.
| Temperature | Last spring: 90% / 50% / 10% chance | First fall: 10% / 50% / 90% chance | Growing season (50%) | Years with at least one |
|---|---|---|---|---|
| Light frost (36°F) | May 21 · Jun 8 · Jun 24 | Aug 29 · Sep 13 · Sep 30 | 95 days | 100% |
| Frost / freeze (32°F) | May 4 · May 20 · Jun 9 | Sep 8 · Sep 26 · Oct 11 | 125 days | 100% |
| Hard freeze (28°F) | Apr 16 · May 4 · May 19 | Sep 21 · Oct 9 · Oct 25 | 157 days | 100% |
Planting calendar for American Falls
Planting windows from the University of Maryland Extension calendar, shifted to your average frost dates. Use them as a starting point and adjust for seed packet instructions and local conditions.
| Crop | Task | Window |
|---|---|---|
| Tomatoes | Start seeds indoors | Apr 19 – Jun 25 |
| Tomatoes | Transplant outdoors | Jun 5 – Jun 6 |
| Peppers | Start seeds indoors | Apr 19 – May 20 |
| Peppers | Transplant outdoors | Jun 19 – Jul 20 |
| Eggplant | Start seeds indoors | May 6 – Jun 4 |
| Eggplant | Transplant outdoors | Jun 19 – Jul 20 |
| Cucumbers | Sow outdoors | Jun 19 – Jun 16 |
| Summer squash | Sow outdoors | Jun 5 – Jul 20 |
| Winter squash & pumpkins | Sow outdoors | Jun 19 – Jul 20 |
| Snap beans | Sow outdoors | Jun 5 – Jul 9 |
| Sweet corn | Sow outdoors | Jun 5 – Jun 6 |
| Watermelon & cantaloupe | Sow outdoors | Jun 19 – Jul 20 |
| Okra | Sow outdoors | Jun 12 – Jul 5 |
| Peas | Sow outdoors (spring) | Apr 19 – Jun 4 |
| Potatoes | Plant outdoors (spring) | Apr 19 – Jun 19 |
| Onions | Start seeds indoors (spring) | Mar 8 – Apr 4 |
| Onions | Transplant outdoors (spring) | May 6 – Jun 4 |
| Broccoli | Start seeds indoors (spring) | Apr 1 – May 5 |
| Broccoli | Transplant outdoors (spring) | May 6 – Jun 4 |
| Broccoli | Start seeds indoors (fall) | May 27 – Jun 6 |
| Broccoli | Transplant outdoors (fall) | Jun 26 – Jul 7 |
| Cabbage | Start seeds indoors (spring) | Mar 22 – Apr 19 |
| Cabbage | Transplant outdoors (spring) | Apr 19 – May 20 |
| Cabbage | Start seeds indoors (fall) | May 17 – Jun 16 |
| Cabbage | Transplant outdoors (fall) | Jun 16 – Jul 17 |
| Leaf lettuce | Sow outdoors (spring) | Apr 19 – Jul 5 |
| Leaf lettuce | Sow outdoors (fall) | Jun 16 – Aug 2 |
| Spinach | Sow outdoors (spring) | Apr 12 – May 26 |
| Spinach | Sow outdoors (fall) | Jul 3 – Aug 7 |
| Radishes | Sow outdoors (spring) | Apr 19 – Jun 9 |
| Radishes | Sow outdoors (fall) | Jun 16 – Aug 17 |
| Kale | Sow outdoors (spring) | May 6 – May 26 |
| Kale | Sow outdoors (fall) | Jun 9 – Jul 17 |
| Carrots | Sow outdoors (spring) | May 20 – Jul 5 |
| Carrots | Sow outdoors (fall) | May 17 – Jul 2 |
| Garlic | Plant outdoors (fall) | Sep 16 – Oct 17 |
Where these dates come from
ZIP code 83211 is matched to the NOAA station Massacre Rocks Sp, ID, 5.6 km away, at 4,195 ft elevation (444 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Massacre Rocks Sp, ID (used) | 4,195 ft | May 20 | Sep 26 |
| American Falls, ID | 4,510 ft | May 4 | Oct 8 |
| American Falls 6 Ne, ID | 4,415 ft | May 14 | Oct 2 |
| Aberdeen Exp Stn, ID | 4,405 ft | May 21 | Sep 20 |
Frost dates near American Falls
- Rockland, ID 83271 · last May 20, first Sep 26
- Arbon, ID 83212 · last May 23, first Sep 24
- Declo, ID 83323 · last Jun 5, first Sep 13
- Aberdeen, ID 83210 · last May 21, first Sep 20
- Pocatello, ID 83204 · last May 16, first Oct 2
- Minidoka, ID 83343 · last May 16, first Oct 1
- Springfield, ID 83277 · last May 21, first Sep 20
- Malta, ID 83342 · last Jun 5, first Sep 13
Frequently asked questions
- When is the last frost in American Falls, ID?
- For ZIP code 83211, the average last spring frost (32°F) is May 20, based on NOAA 1991-2020 climate normals for the Massacre Rocks Sp, ID weather station. There is a 1-in-10 chance of a frost after June 9.
- When is the first frost in American Falls, ID?
- The average first fall frost (32°F) is September 26. There is a 1-in-10 chance of frost by September 8, so tender plants are at risk from that point on.
- How long is the growing season in 83211?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 125 days long.
- Are these frost dates a forecast?
- No. They are 30-year averages and probabilities from NOAA weather station records. Use them to plan, then watch your local forecast before planting tender crops or leaving them uncovered.