Frost dates for 83251Mackay, ID
The average last spring frost in Mackay is June 1 and the average first fall frost is September 20, giving a typical growing season of about 109 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Jun 1
- Average first fall frost
- Sep 20
- Growing season
- 109 days
Safer after Jun 21 (1-in-10 risk)
Possible by Sep 4 (1-in-10 risk)
Last frost typically in 210 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) | Jun 1 · Jun 18 · Jul 3 | Aug 24 · Sep 6 · Sep 22 | 80 days | 100% |
| Frost / freeze (32°F) | May 13 · Jun 1 · Jun 21 | Sep 4 · Sep 20 · Oct 3 | 109 days | 100% |
| Hard freeze (28°F) | Apr 30 · May 13 · Jun 4 | Sep 16 · Oct 1 · Oct 15 | 138 days | 100% |
Planting calendar for Mackay
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 | May 1 – Jul 7 |
| Tomatoes | Transplant outdoors | Jun 17 – May 31 |
| Peppers | Start seeds indoors | May 1 – Jun 1 |
| Peppers | Transplant outdoors | Jul 1 – Aug 1 |
| Eggplant | Start seeds indoors | May 18 – Jun 16 |
| Eggplant | Transplant outdoors | Jul 1 – Aug 1 |
| Cucumbers | Sow outdoors | Jul 1 – Jun 10 |
| Summer squash | Sow outdoors | Jun 17 – Aug 1 |
| Winter squash & pumpkins | Sow outdoors | Jul 1 – Aug 1 |
| Snap beans | Sow outdoors | Jun 17 – Jul 3 |
| Sweet corn | Sow outdoors | Jun 17 – May 31 |
| Watermelon & cantaloupe | Sow outdoors | Jul 1 – Aug 1 |
| Okra | Sow outdoors | Jun 24 – Jul 17 |
| Peas | Sow outdoors (spring) | May 1 – Jun 16 |
| Potatoes | Plant outdoors (spring) | May 1 – Jul 1 |
| Onions | Start seeds indoors (spring) | Mar 20 – Apr 16 |
| Onions | Transplant outdoors (spring) | May 18 – Jun 16 |
| Broccoli | Start seeds indoors (spring) | Apr 13 – May 17 |
| Broccoli | Transplant outdoors (spring) | May 18 – Jun 16 |
| Broccoli | Start seeds indoors (fall) | May 21 – May 31 |
| Broccoli | Transplant outdoors (fall) | Jun 20 – Jul 1 |
| Cabbage | Start seeds indoors (spring) | Apr 3 – May 1 |
| Cabbage | Transplant outdoors (spring) | May 1 – Jun 1 |
| Cabbage | Start seeds indoors (fall) | May 11 – Jun 10 |
| Cabbage | Transplant outdoors (fall) | Jun 10 – Jul 11 |
| Leaf lettuce | Sow outdoors (spring) | May 1 – Jul 17 |
| Leaf lettuce | Sow outdoors (fall) | Jun 10 – Jul 27 |
| Spinach | Sow outdoors (spring) | Apr 24 – Jun 7 |
| Spinach | Sow outdoors (fall) | Jun 27 – Aug 1 |
| Radishes | Sow outdoors (spring) | May 1 – Jun 21 |
| Radishes | Sow outdoors (fall) | Jun 10 – Aug 11 |
| Kale | Sow outdoors (spring) | May 18 – Jun 7 |
| Kale | Sow outdoors (fall) | Jun 3 – Jul 11 |
| Carrots | Sow outdoors (spring) | Jun 1 – Jul 17 |
| Carrots | Sow outdoors (fall) | May 11 – Jun 26 |
| Garlic | Plant outdoors (fall) | Sep 10 – Oct 11 |
Where these dates come from
ZIP code 83251 is matched to the NOAA station Mackay Lost Rvr Rs, ID, 0.8 km away, at 5,897 ft elevation (5 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Mackay Lost Rvr Rs, ID (used) | 5,897 ft | Jun 1 | Sep 20 |
| Chilly Barton Flat, ID | 6,260 ft | Jun 14 | Sep 8 |
| Arco, ID | 5,325 ft | May 22 | Sep 22 |
| Craters Of The Moon, ID | 5,914 ft | Jun 19 | Sep 9 |
Frost dates near Mackay
- Moore, ID 83255 · last Jun 14, first Sep 8
- Arco, ID 83213 · last May 22, first Sep 22
- Howe, ID 83244 · last May 24, first Sep 14
- Sun Valley, ID 83353 · last —, first —
- Hailey, ID 83333 · last May 13, first Oct 2
- Bellevue, ID 83313 · last May 13, first Oct 2
- Carey, ID 83320 · last Jun 16, first Sep 9
- Ketchum, ID 83340 · last —, first —
Frequently asked questions
- When is the last frost in Mackay, ID?
- For ZIP code 83251, the average last spring frost (32°F) is June 1, based on NOAA 1991-2020 climate normals for the Mackay Lost Rvr Rs, ID weather station. There is a 1-in-10 chance of a frost after June 21.
- When is the first frost in Mackay, ID?
- The average first fall frost (32°F) is September 20. There is a 1-in-10 chance of frost by September 4, so tender plants are at risk from that point on.
- How long is the growing season in 83251?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 109 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.