Frost dates for 83705Boise, ID
The average last spring frost in Boise is April 24 and the average first fall frost is October 21, giving a typical growing season of about 179 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Apr 24
- Average first fall frost
- Oct 21
- Growing season
- 179 days
Safer after May 9 (1-in-10 risk)
Possible by Oct 5 (1-in-10 risk)
Last frost typically in 179 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) | Apr 23 · May 8 · May 29 | Sep 25 · Oct 8 · Oct 25 | 153 days | 100% |
| Frost / freeze (32°F) | Apr 4 · Apr 24 · May 9 | Oct 5 · Oct 21 · Nov 5 | 179 days | 100% |
| Hard freeze (28°F) | Mar 10 · Apr 2 · Apr 25 | Oct 17 · Oct 31 · Nov 19 | 212 days | 100% |
Planting calendar for Boise
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 | Mar 24 – May 30 |
| Tomatoes | Transplant outdoors | May 10 – Jul 1 |
| Peppers | Start seeds indoors | Mar 24 – Apr 24 |
| Peppers | Transplant outdoors | May 24 – Jun 24 |
| Eggplant | Start seeds indoors | Apr 10 – May 9 |
| Eggplant | Transplant outdoors | May 24 – Jun 24 |
| Cucumbers | Sow outdoors | May 24 – Jul 11 |
| Summer squash | Sow outdoors | May 10 – Jun 24 |
| Winter squash & pumpkins | Sow outdoors | May 24 – Jun 24 |
| Snap beans | Sow outdoors | May 10 – Aug 3 |
| Sweet corn | Sow outdoors | May 10 – Jul 1 |
| Watermelon & cantaloupe | Sow outdoors | May 24 – Jun 24 |
| Okra | Sow outdoors | May 17 – Jun 9 |
| Peas | Sow outdoors (spring) | Mar 24 – May 9 |
| Potatoes | Plant outdoors (spring) | Mar 24 – May 24 |
| Onions | Start seeds indoors (spring) | Feb 10 – Mar 9 |
| Onions | Transplant outdoors (spring) | Apr 10 – May 9 |
| Broccoli | Start seeds indoors (spring) | Mar 6 – Apr 9 |
| Broccoli | Transplant outdoors (spring) | Apr 10 – May 9 |
| Broccoli | Start seeds indoors (fall) | Jun 21 – Jul 1 |
| Broccoli | Transplant outdoors (fall) | Jul 21 – Aug 1 |
| Cabbage | Start seeds indoors (spring) | Feb 24 – Mar 24 |
| Cabbage | Transplant outdoors (spring) | Mar 24 – Apr 24 |
| Cabbage | Start seeds indoors (fall) | Jun 11 – Jul 11 |
| Cabbage | Transplant outdoors (fall) | Jul 11 – Aug 11 |
| Leaf lettuce | Sow outdoors (spring) | Mar 24 – Jun 9 |
| Leaf lettuce | Sow outdoors (fall) | Jul 11 – Aug 27 |
| Spinach | Sow outdoors (spring) | Mar 17 – Apr 30 |
| Spinach | Sow outdoors (fall) | Jul 28 – Sep 1 |
| Radishes | Sow outdoors (spring) | Mar 24 – May 14 |
| Radishes | Sow outdoors (fall) | Jul 11 – Sep 11 |
| Kale | Sow outdoors (spring) | Apr 10 – Apr 30 |
| Kale | Sow outdoors (fall) | Jul 4 – Aug 11 |
| Carrots | Sow outdoors (spring) | Apr 24 – Jun 9 |
| Carrots | Sow outdoors (fall) | Jun 11 – Jul 27 |
| Garlic | Plant outdoors (fall) | Oct 11 – Nov 11 |
Where these dates come from
ZIP code 83705 is matched to the NOAA station Boise Air Terminal, ID, 2.7 km away, at 2,814 ft elevation (55 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Boise Air Terminal, ID (used) | 2,814 ft | Apr 24 | Oct 21 |
| Boise Lucky Peak Dam, ID | 2,840 ft | Apr 30 | Oct 22 |
| Boise 7 N, ID | 3,885 ft | May 17 | Oct 12 |
| Arrowrock Dam, ID | 3,235 ft | Apr 28 | Oct 14 |
Frost dates near Boise
- Boise, ID 83706 · last Apr 24, first Oct 21
- Meridian, ID 83680 · last Apr 29, first Oct 13
- Garden City, ID 83714 · last Apr 24, first Oct 21
- Kuna, ID 83634 · last Apr 24, first Oct 21
- Eagle, ID 83616 · last Apr 29, first Oct 13
- Nampa, ID 83687 · last Apr 29, first Oct 13
- Star, ID 83669 · last Apr 29, first Oct 13
- Mountain Home Afb, ID 83648 · last Apr 30, first Oct 17
Frequently asked questions
- When is the last frost in Boise, ID?
- For ZIP code 83705, the average last spring frost (32°F) is April 24, based on NOAA 1991-2020 climate normals for the Boise Air Terminal, ID weather station. There is a 1-in-10 chance of a frost after May 9.
- When is the first frost in Boise, ID?
- The average first fall frost (32°F) is October 21. There is a 1-in-10 chance of frost by October 5, so tender plants are at risk from that point on.
- How long is the growing season in 83705?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 179 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.