Frost dates for 59801Missoula, MT
The average last spring frost in Missoula is May 16 and the average first fall frost is September 26, giving a typical growing season of about 130 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 16
- Average first fall frost
- Sep 26
- Growing season
- 130 days
Safer after Jun 1 (1-in-10 risk)
Possible by Sep 12 (1-in-10 risk)
Last frost typically in 201 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 22 · Jun 7 · Jun 25 | Aug 30 · Sep 14 · Sep 28 | 96 days | 100% |
| Frost / freeze (32°F) | May 3 · May 16 · Jun 1 | Sep 12 · Sep 26 · Oct 8 | 130 days | 100% |
| Hard freeze (28°F) | Apr 17 · May 2 · May 14 | Sep 24 · Oct 6 · Oct 19 | 156 days | 100% |
Planting calendar for Missoula
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 15 – Jun 21 |
| Tomatoes | Transplant outdoors | Jun 1 – Jun 6 |
| Peppers | Start seeds indoors | Apr 15 – May 16 |
| Peppers | Transplant outdoors | Jun 15 – Jul 16 |
| Eggplant | Start seeds indoors | May 2 – May 31 |
| Eggplant | Transplant outdoors | Jun 15 – Jul 16 |
| Cucumbers | Sow outdoors | Jun 15 – Jun 16 |
| Summer squash | Sow outdoors | Jun 1 – Jul 16 |
| Winter squash & pumpkins | Sow outdoors | Jun 15 – Jul 16 |
| Snap beans | Sow outdoors | Jun 1 – Jul 9 |
| Sweet corn | Sow outdoors | Jun 1 – Jun 6 |
| Watermelon & cantaloupe | Sow outdoors | Jun 15 – Jul 16 |
| Okra | Sow outdoors | Jun 8 – Jul 1 |
| Peas | Sow outdoors (spring) | Apr 15 – May 31 |
| Potatoes | Plant outdoors (spring) | Apr 15 – Jun 15 |
| Onions | Start seeds indoors (spring) | Mar 4 – Mar 31 |
| Onions | Transplant outdoors (spring) | May 2 – May 31 |
| Broccoli | Start seeds indoors (spring) | Mar 28 – May 1 |
| Broccoli | Transplant outdoors (spring) | May 2 – May 31 |
| Broccoli | Start seeds indoors (fall) | May 27 – Jun 6 |
| Broccoli | Transplant outdoors (fall) | Jun 26 – Jul 7 |
| Cabbage | Start seeds indoors (spring) | Mar 18 – Apr 15 |
| Cabbage | Transplant outdoors (spring) | Apr 15 – May 16 |
| Cabbage | Start seeds indoors (fall) | May 17 – Jun 16 |
| Cabbage | Transplant outdoors (fall) | Jun 16 – Jul 17 |
| Leaf lettuce | Sow outdoors (spring) | Apr 15 – Jul 1 |
| Leaf lettuce | Sow outdoors (fall) | Jun 16 – Aug 2 |
| Spinach | Sow outdoors (spring) | Apr 8 – May 22 |
| Spinach | Sow outdoors (fall) | Jul 3 – Aug 7 |
| Radishes | Sow outdoors (spring) | Apr 15 – Jun 5 |
| Radishes | Sow outdoors (fall) | Jun 16 – Aug 17 |
| Kale | Sow outdoors (spring) | May 2 – May 22 |
| Kale | Sow outdoors (fall) | Jun 9 – Jul 17 |
| Carrots | Sow outdoors (spring) | May 16 – Jul 1 |
| Carrots | Sow outdoors (fall) | May 17 – Jul 2 |
| Garlic | Plant outdoors (fall) | Sep 16 – Oct 17 |
Where these dates come from
ZIP code 59801 is matched to the NOAA station Missoula Intl Ap, MT, 8.8 km away, at 3,192 ft elevation (10 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Missoula Intl Ap, MT (used) | 3,192 ft | May 16 | Sep 26 |
| Missoula 2 Ne, MT | 3,420 ft | May 10 | Oct 1 |
| Missoula 6 Nw Wfo, MT | 3,197 ft | May 6 | Oct 4 |
| Potomac, MT | 3,690 ft | — | — |
Frost dates near Missoula
- Missoula, MT 59806 · last May 6, first Oct 4
- Milltown, MT 59851 · last May 10, first Oct 1
- Bonner, MT 59823 · last May 10, first Oct 1
- Lolo, MT 59847 · last May 16, first Sep 26
- Florence, MT 59833 · last May 22, first Sep 19
- Clinton, MT 59825 · last —, first —
- Frenchtown, MT 59834 · last May 10, first Oct 1
- Stevensville, MT 59870 · last May 22, first Sep 19
Frequently asked questions
- When is the last frost in Missoula, MT?
- For ZIP code 59801, the average last spring frost (32°F) is May 16, based on NOAA 1991-2020 climate normals for the Missoula Intl Ap, MT weather station. There is a 1-in-10 chance of a frost after June 1.
- When is the first frost in Missoula, MT?
- The average first fall frost (32°F) is September 26. There is a 1-in-10 chance of frost by September 12, so tender plants are at risk from that point on.
- How long is the growing season in 59801?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 130 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.