Frost dates for 59807Missoula, MT
The average last spring frost in Missoula is May 10 and the average first fall frost is October 1, giving a typical growing season of about 143 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 10
- Average first fall frost
- Oct 1
- Growing season
- 143 days
Safer after May 28 (1-in-10 risk)
Possible by Sep 16 (1-in-10 risk)
Last frost typically in 196 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 12 · Jun 1 · Jun 24 | Sep 3 · Sep 19 · Oct 2 | 109 days | 100% |
| Frost / freeze (32°F) | Apr 27 · May 10 · May 28 | Sep 16 · Oct 1 · Oct 15 | 143 days | 100% |
| Hard freeze (28°F) | Apr 12 · Apr 28 · May 11 | Sep 28 · Oct 12 · Oct 25 | 167 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 9 – Jun 15 |
| Tomatoes | Transplant outdoors | May 26 – Jun 11 |
| Peppers | Start seeds indoors | Apr 9 – May 10 |
| Peppers | Transplant outdoors | Jun 9 – Jul 10 |
| Eggplant | Start seeds indoors | Apr 26 – May 25 |
| Eggplant | Transplant outdoors | Jun 9 – Jul 10 |
| Cucumbers | Sow outdoors | Jun 9 – Jun 21 |
| Summer squash | Sow outdoors | May 26 – Jul 10 |
| Winter squash & pumpkins | Sow outdoors | Jun 9 – Jul 10 |
| Snap beans | Sow outdoors | May 26 – Jul 14 |
| Sweet corn | Sow outdoors | May 26 – Jun 11 |
| Watermelon & cantaloupe | Sow outdoors | Jun 9 – Jul 10 |
| Okra | Sow outdoors | Jun 2 – Jun 25 |
| Peas | Sow outdoors (spring) | Apr 9 – May 25 |
| Potatoes | Plant outdoors (spring) | Apr 9 – Jun 9 |
| Onions | Start seeds indoors (spring) | Feb 26 – Mar 25 |
| Onions | Transplant outdoors (spring) | Apr 26 – May 25 |
| Broccoli | Start seeds indoors (spring) | Mar 22 – Apr 25 |
| Broccoli | Transplant outdoors (spring) | Apr 26 – May 25 |
| Broccoli | Start seeds indoors (fall) | Jun 1 – Jun 11 |
| Broccoli | Transplant outdoors (fall) | Jul 1 – Jul 12 |
| Cabbage | Start seeds indoors (spring) | Mar 12 – Apr 9 |
| Cabbage | Transplant outdoors (spring) | Apr 9 – May 10 |
| Cabbage | Start seeds indoors (fall) | May 22 – Jun 21 |
| Cabbage | Transplant outdoors (fall) | Jun 21 – Jul 22 |
| Leaf lettuce | Sow outdoors (spring) | Apr 9 – Jun 25 |
| Leaf lettuce | Sow outdoors (fall) | Jun 21 – Aug 7 |
| Spinach | Sow outdoors (spring) | Apr 2 – May 16 |
| Spinach | Sow outdoors (fall) | Jul 8 – Aug 12 |
| Radishes | Sow outdoors (spring) | Apr 9 – May 30 |
| Radishes | Sow outdoors (fall) | Jun 21 – Aug 22 |
| Kale | Sow outdoors (spring) | Apr 26 – May 16 |
| Kale | Sow outdoors (fall) | Jun 14 – Jul 22 |
| Carrots | Sow outdoors (spring) | May 10 – Jun 25 |
| Carrots | Sow outdoors (fall) | May 22 – Jul 7 |
| Garlic | Plant outdoors (fall) | Sep 21 – Oct 22 |
Where these dates come from
ZIP code 59807 is matched to the NOAA station Missoula 2 Ne, MT, 1.5 km away, at 3,420 ft elevation (100 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Missoula 2 Ne, MT (used) | 3,420 ft | May 10 | Oct 1 |
| Missoula 6 Nw Wfo, MT | 3,197 ft | May 6 | Oct 4 |
| Missoula Intl Ap, MT | 3,192 ft | May 16 | Sep 26 |
| Potomac, MT | 3,690 ft | — | — |
Frost dates near Missoula
- Missoula, MT 59802 · last May 10, first Oct 1
- 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 —
- Frenchtown, MT 59834 · last May 10, first Oct 1
- Arlee, MT 59821 · last May 12, first Oct 2
- Florence, MT 59833 · last May 22, first Sep 19
Frequently asked questions
- When is the last frost in Missoula, MT?
- For ZIP code 59807, the average last spring frost (32°F) is May 10, based on NOAA 1991-2020 climate normals for the Missoula 2 Ne, MT weather station. There is a 1-in-10 chance of a frost after May 28.
- When is the first frost in Missoula, MT?
- The average first fall frost (32°F) is October 1. 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 59807?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 143 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.