Frost dates for 59812Missoula, MT
The average last spring frost in Missoula is May 6 and the average first fall frost is October 4, giving a typical growing season of about 151 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 6
- Average first fall frost
- Oct 4
- Growing season
- 151 days
Safer after May 19 (1-in-10 risk)
Possible by Sep 23 (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 7 · May 23 · Jun 10 | Sep 11 · Sep 25 · Oct 5 | 123 days | 100% |
| Frost / freeze (32°F) | Apr 24 · May 6 · May 19 | Sep 23 · Oct 4 · Oct 16 | 151 days | 100% |
| Hard freeze (28°F) | Apr 6 · Apr 23 · May 7 | Oct 3 · Oct 15 · Oct 29 | 176 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 5 – Jun 11 |
| Tomatoes | Transplant outdoors | May 22 – Jun 14 |
| Peppers | Start seeds indoors | Apr 5 – May 6 |
| Peppers | Transplant outdoors | Jun 5 – Jul 6 |
| Eggplant | Start seeds indoors | Apr 22 – May 21 |
| Eggplant | Transplant outdoors | Jun 5 – Jul 6 |
| Cucumbers | Sow outdoors | Jun 5 – Jun 24 |
| Summer squash | Sow outdoors | May 22 – Jul 6 |
| Winter squash & pumpkins | Sow outdoors | Jun 5 – Jul 6 |
| Snap beans | Sow outdoors | May 22 – Jul 17 |
| Sweet corn | Sow outdoors | May 22 – Jun 14 |
| Watermelon & cantaloupe | Sow outdoors | Jun 5 – Jul 6 |
| Okra | Sow outdoors | May 29 – Jun 21 |
| Peas | Sow outdoors (spring) | Apr 5 – May 21 |
| Potatoes | Plant outdoors (spring) | Apr 5 – Jun 5 |
| Onions | Start seeds indoors (spring) | Feb 22 – Mar 21 |
| Onions | Transplant outdoors (spring) | Apr 22 – May 21 |
| Broccoli | Start seeds indoors (spring) | Mar 18 – Apr 21 |
| Broccoli | Transplant outdoors (spring) | Apr 22 – May 21 |
| Broccoli | Start seeds indoors (fall) | Jun 4 – Jun 14 |
| Broccoli | Transplant outdoors (fall) | Jul 4 – Jul 15 |
| Cabbage | Start seeds indoors (spring) | Mar 8 – Apr 5 |
| Cabbage | Transplant outdoors (spring) | Apr 5 – May 6 |
| Cabbage | Start seeds indoors (fall) | May 25 – Jun 24 |
| Cabbage | Transplant outdoors (fall) | Jun 24 – Jul 25 |
| Leaf lettuce | Sow outdoors (spring) | Apr 5 – Jun 21 |
| Leaf lettuce | Sow outdoors (fall) | Jun 24 – Aug 10 |
| Spinach | Sow outdoors (spring) | Mar 29 – May 12 |
| Spinach | Sow outdoors (fall) | Jul 11 – Aug 15 |
| Radishes | Sow outdoors (spring) | Apr 5 – May 26 |
| Radishes | Sow outdoors (fall) | Jun 24 – Aug 25 |
| Kale | Sow outdoors (spring) | Apr 22 – May 12 |
| Kale | Sow outdoors (fall) | Jun 17 – Jul 25 |
| Carrots | Sow outdoors (spring) | May 6 – Jun 21 |
| Carrots | Sow outdoors (fall) | May 25 – Jul 10 |
| Garlic | Plant outdoors (fall) | Sep 24 – Oct 25 |
Where these dates come from
ZIP code 59812 is matched to the NOAA station Missoula 6 Nw Wfo, MT, 9.4 km away, at 3,197 ft elevation (12 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Missoula 6 Nw Wfo, MT (used) | 3,197 ft | May 6 | Oct 4 |
| Missoula 2 Ne, MT | 3,420 ft | May 10 | Oct 1 |
| Missoula Intl Ap, MT | 3,192 ft | May 16 | Sep 26 |
| 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
- Clinton, MT 59825 · last —, first —
- Florence, MT 59833 · last May 22, first Sep 19
- Frenchtown, MT 59834 · last May 10, first Oct 1
- Arlee, MT 59821 · last May 12, first Oct 2
Frequently asked questions
- When is the last frost in Missoula, MT?
- For ZIP code 59812, the average last spring frost (32°F) is May 6, based on NOAA 1991-2020 climate normals for the Missoula 6 Nw Wfo, MT weather station. There is a 1-in-10 chance of a frost after May 19.
- When is the first frost in Missoula, MT?
- The average first fall frost (32°F) is October 4. There is a 1-in-10 chance of frost by September 23, so tender plants are at risk from that point on.
- How long is the growing season in 59812?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 151 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.