Frost dates for 83403Idaho Falls, ID
The average last spring frost in Idaho Falls is May 9 and the average first fall frost is October 1, giving a typical growing season of about 142 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 9
- Average first fall frost
- Oct 1
- Growing season
- 142 days
Safer after Jun 2 (1-in-10 risk)
Possible by Sep 17 (1-in-10 risk)
Last frost typically in 187 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 10 · May 30 · Jun 16 | Sep 4 · Sep 20 · Oct 3 | 113 days | 100% |
| Frost / freeze (32°F) | Apr 27 · May 9 · Jun 2 | Sep 17 · Oct 1 · Oct 15 | 142 days | 100% |
| Hard freeze (28°F) | Apr 11 · Apr 28 · May 11 | Sep 27 · Oct 13 · Oct 27 | 168 days | 100% |
Planting calendar for Idaho 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 8 – Jun 14 |
| Tomatoes | Transplant outdoors | May 25 – Jun 11 |
| Peppers | Start seeds indoors | Apr 8 – May 9 |
| Peppers | Transplant outdoors | Jun 8 – Jul 9 |
| Eggplant | Start seeds indoors | Apr 25 – May 24 |
| Eggplant | Transplant outdoors | Jun 8 – Jul 9 |
| Cucumbers | Sow outdoors | Jun 8 – Jun 21 |
| Summer squash | Sow outdoors | May 25 – Jul 9 |
| Winter squash & pumpkins | Sow outdoors | Jun 8 – Jul 9 |
| Snap beans | Sow outdoors | May 25 – Jul 14 |
| Sweet corn | Sow outdoors | May 25 – Jun 11 |
| Watermelon & cantaloupe | Sow outdoors | Jun 8 – Jul 9 |
| Okra | Sow outdoors | Jun 1 – Jun 24 |
| Peas | Sow outdoors (spring) | Apr 8 – May 24 |
| Potatoes | Plant outdoors (spring) | Apr 8 – Jun 8 |
| Onions | Start seeds indoors (spring) | Feb 25 – Mar 24 |
| Onions | Transplant outdoors (spring) | Apr 25 – May 24 |
| Broccoli | Start seeds indoors (spring) | Mar 21 – Apr 24 |
| Broccoli | Transplant outdoors (spring) | Apr 25 – May 24 |
| Broccoli | Start seeds indoors (fall) | Jun 1 – Jun 11 |
| Broccoli | Transplant outdoors (fall) | Jul 1 – Jul 12 |
| Cabbage | Start seeds indoors (spring) | Mar 11 – Apr 8 |
| Cabbage | Transplant outdoors (spring) | Apr 8 – May 9 |
| Cabbage | Start seeds indoors (fall) | May 22 – Jun 21 |
| Cabbage | Transplant outdoors (fall) | Jun 21 – Jul 22 |
| Leaf lettuce | Sow outdoors (spring) | Apr 8 – Jun 24 |
| Leaf lettuce | Sow outdoors (fall) | Jun 21 – Aug 7 |
| Spinach | Sow outdoors (spring) | Apr 1 – May 15 |
| Spinach | Sow outdoors (fall) | Jul 8 – Aug 12 |
| Radishes | Sow outdoors (spring) | Apr 8 – May 29 |
| Radishes | Sow outdoors (fall) | Jun 21 – Aug 22 |
| Kale | Sow outdoors (spring) | Apr 25 – May 15 |
| Kale | Sow outdoors (fall) | Jun 14 – Jul 22 |
| Carrots | Sow outdoors (spring) | May 9 – Jun 24 |
| Carrots | Sow outdoors (fall) | May 22 – Jul 7 |
| Garlic | Plant outdoors (fall) | Sep 21 – Oct 22 |
Where these dates come from
ZIP code 83403 is matched to the NOAA station Idaho Falls - Kifi, ID, 5.5 km away, at 4,742 ft elevation (34 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Idaho Falls - Kifi, ID (used) | 4,742 ft | May 9 | Oct 1 |
| Idaho Falls Fanning Fld, ID | 4,729 ft | May 23 | Sep 20 |
| Idaho Falls 16 Se, ID | 5,828 ft | Jun 9 | Sep 11 |
| Rigby, ID | 4,856 ft | May 9 | Oct 5 |
Frost dates near Idaho Falls
- Idaho Falls, ID 83405 · last May 9, first Oct 1
- Iona, ID 83427 · last May 9, first Oct 1
- Shelley, ID 83274 · last May 23, first Sep 20
- Ucon, ID 83454 · last May 9, first Oct 1
- Basalt, ID 83218 · last May 5, first Oct 3
- Firth, ID 83236 · last May 5, first Oct 3
- Lewisville, ID 83431 · last May 9, first Oct 1
- Rigby, ID 83442 · last May 9, first Oct 5
Frequently asked questions
- When is the last frost in Idaho Falls, ID?
- For ZIP code 83403, the average last spring frost (32°F) is May 9, based on NOAA 1991-2020 climate normals for the Idaho Falls - Kifi, ID weather station. There is a 1-in-10 chance of a frost after June 2.
- When is the first frost in Idaho Falls, ID?
- The average first fall frost (32°F) is October 1. There is a 1-in-10 chance of frost by September 17, so tender plants are at risk from that point on.
- How long is the growing season in 83403?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 142 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.