Frost dates for 83221Blackfoot, ID
The average last spring frost in Blackfoot is May 5 and the average first fall frost is October 3, giving a typical growing season of about 149 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 5
- Average first fall frost
- Oct 3
- Growing season
- 149 days
Safer after May 22 (1-in-10 risk)
Possible by Sep 16 (1-in-10 risk)
Last frost typically in 185 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 8 · May 23 · Jun 14 | Sep 4 · Sep 21 · Oct 5 | 118 days | 100% |
| Frost / freeze (32°F) | Apr 23 · May 5 · May 22 | Sep 16 · Oct 3 · Oct 18 | 149 days | 100% |
| Hard freeze (28°F) | Apr 6 · Apr 22 · May 4 | Sep 30 · Oct 16 · Oct 31 | 176 days | 100% |
Planting calendar for Blackfoot
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 4 – Jun 10 |
| Tomatoes | Transplant outdoors | May 21 – Jun 13 |
| Peppers | Start seeds indoors | Apr 4 – May 5 |
| Peppers | Transplant outdoors | Jun 4 – Jul 5 |
| Eggplant | Start seeds indoors | Apr 21 – May 20 |
| Eggplant | Transplant outdoors | Jun 4 – Jul 5 |
| Cucumbers | Sow outdoors | Jun 4 – Jun 23 |
| Summer squash | Sow outdoors | May 21 – Jul 5 |
| Winter squash & pumpkins | Sow outdoors | Jun 4 – Jul 5 |
| Snap beans | Sow outdoors | May 21 – Jul 16 |
| Sweet corn | Sow outdoors | May 21 – Jun 13 |
| Watermelon & cantaloupe | Sow outdoors | Jun 4 – Jul 5 |
| Okra | Sow outdoors | May 28 – Jun 20 |
| Peas | Sow outdoors (spring) | Apr 4 – May 20 |
| Potatoes | Plant outdoors (spring) | Apr 4 – Jun 4 |
| Onions | Start seeds indoors (spring) | Feb 21 – Mar 20 |
| Onions | Transplant outdoors (spring) | Apr 21 – May 20 |
| Broccoli | Start seeds indoors (spring) | Mar 17 – Apr 20 |
| Broccoli | Transplant outdoors (spring) | Apr 21 – May 20 |
| Broccoli | Start seeds indoors (fall) | Jun 3 – Jun 13 |
| Broccoli | Transplant outdoors (fall) | Jul 3 – Jul 14 |
| Cabbage | Start seeds indoors (spring) | Mar 7 – Apr 4 |
| Cabbage | Transplant outdoors (spring) | Apr 4 – May 5 |
| Cabbage | Start seeds indoors (fall) | May 24 – Jun 23 |
| Cabbage | Transplant outdoors (fall) | Jun 23 – Jul 24 |
| Leaf lettuce | Sow outdoors (spring) | Apr 4 – Jun 20 |
| Leaf lettuce | Sow outdoors (fall) | Jun 23 – Aug 9 |
| Spinach | Sow outdoors (spring) | Mar 28 – May 11 |
| Spinach | Sow outdoors (fall) | Jul 10 – Aug 14 |
| Radishes | Sow outdoors (spring) | Apr 4 – May 25 |
| Radishes | Sow outdoors (fall) | Jun 23 – Aug 24 |
| Kale | Sow outdoors (spring) | Apr 21 – May 11 |
| Kale | Sow outdoors (fall) | Jun 16 – Jul 24 |
| Carrots | Sow outdoors (spring) | May 5 – Jun 20 |
| Carrots | Sow outdoors (fall) | May 24 – Jul 9 |
| Garlic | Plant outdoors (fall) | Sep 23 – Oct 24 |
Where these dates come from
ZIP code 83221 is matched to the NOAA station Blackfoot Fire Dept, ID, 1.3 km away, at 4,499 ft elevation (11 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Blackfoot Fire Dept, ID (used) | 4,499 ft | May 5 | Oct 3 |
| Ft Hall 1 Nne, ID | 4,465 ft | May 20 | Sep 20 |
| Pocatello 2 Ne, ID | 4,832 ft | May 16 | Oct 2 |
| Pocatello Rgnl Ap, ID | 4,478 ft | May 23 | Sep 18 |
Frost dates near Blackfoot
- Moreland, ID 83256 · last May 5, first Oct 3
- Fort Hall, ID 83203 · last May 20, first Sep 20
- Firth, ID 83236 · last May 5, first Oct 3
- Basalt, ID 83218 · last May 5, first Oct 3
- Pingree, ID 83262 · last May 20, first Sep 20
- Springfield, ID 83277 · last May 21, first Sep 20
- Shelley, ID 83274 · last May 23, first Sep 20
- Pocatello, ID 83202 · last May 2, first Oct 11
Frequently asked questions
- When is the last frost in Blackfoot, ID?
- For ZIP code 83221, the average last spring frost (32°F) is May 5, based on NOAA 1991-2020 climate normals for the Blackfoot Fire Dept, ID weather station. There is a 1-in-10 chance of a frost after May 22.
- When is the first frost in Blackfoot, ID?
- The average first fall frost (32°F) is October 3. There is a 1-in-10 chance of frost by September 16, so tender plants are at risk from that point on.
- How long is the growing season in 83221?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 149 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.