Missoula, MT planting zone & frost dates
Missoula is in USDA hardiness zone 5b. The last spring frost usually comes around May 10 and the first fall frost around October 1, for a growing season of about 143 days.
Planting calendar for Missoula
Dates are counted from the average last spring frost (May 10) using the typical timing recommended by U.S. extension services. Warm-season crops go out only after the danger of frost has passed and the soil has warmed.
| Crop | When |
|---|---|
| Tomatoes | Start seeds indoors: Mar 15 – Mar 29 Transplant outdoors: May 17 – May 24 |
| Peppers | Start seeds indoors: Mar 1 – Mar 15 Transplant outdoors: May 24 – May 31 |
| Eggplant | Start seeds indoors: Mar 1 – Mar 15 Transplant outdoors: May 24 – May 31 |
| Broccoli | Start seeds indoors: Mar 1 – Mar 15 Transplant outdoors: Apr 12 – Apr 26 |
| Cabbage | Start seeds indoors: Mar 1 – Mar 15 Transplant outdoors: Apr 12 – Apr 26 |
| Onions (sets) | Plant outdoors: Apr 12 – Apr 26 |
| Peas | Sow outdoors: Mar 29 – Apr 12 |
| Spinach | Sow outdoors: Mar 29 – Apr 12 |
| Lettuce | Sow outdoors: Apr 12 – Apr 26 |
| Carrots | Sow outdoors: Apr 12 – Apr 26 |
| Potatoes | Plant outdoors: Apr 12 – Apr 26 |
| Beans | Sow outdoors: May 17 – May 24 |
| Sweet corn | Sow outdoors: May 17 – May 24 |
| Cucumbers | Sow outdoors: May 17 – May 24 |
| Squash & zucchini | Sow outdoors: May 17 – May 24 |
| Basil | Start seeds indoors: Mar 29 – Apr 12 Transplant outdoors: May 17 – May 24 |
Fall garden: cool-season crops like lettuce, spinach and kale can be sown again around Aug 6 (8 weeks before the average first fall frost on Oct 1).
Useful for zone 5b gardens
- Seed starting kit with dome — to start seeds indoors before the last frost
- LED grow light for seedlings — stops leggy seedlings
- Frost cloth / plant covers — for late spring and early fall frosts
- Soil thermometer — warm-season crops need soil above 60°F
- Cold frame / mini greenhouse — adds weeks to a short season
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Frost risk in detail
| 90% chance | 50% chance | 10% chance | |
|---|---|---|---|
| Last 32°F frost in spring is after | Apr 27 | May 10 | May 28 |
| First 32°F frost in fall is before | Oct 15 | Oct 1 | Sep 16 |
How to read it: in spring there is a 10% chance of a frost after May 28, so that is a safe date for tender plants. In fall there is a 10% chance of frost before September 16. A hard freeze (28°F) usually ends around April 28.
Hardiness zone by ZIP code in Missoula
- 59801 zone 5b
- 59802 zone 5b
- 59803 zone 5b
- 59804 zone 5b
- 59806 zone 5b
- 59807 zone 6a
- 59808 zone 5b
- 59812 zone 5b
Nearby cities
Questions
What growing zone is Missoula, MT?
Missoula is in USDA Plant Hardiness Zone 5b (average extreme winter low -15°F to -10°F), according to the USDA 2023 map. Some ZIP codes of the city fall in zone 6a.
When is the last frost in Missoula?
The average last spring frost (32°F) in Missoula is May 10. There is still a 10% chance of frost until May 28.
When can I plant tomatoes in Missoula?
Transplant tomatoes outdoors 1–2 weeks after the average last frost: around May 17 – May 24. Start seeds indoors 6–8 weeks before the last frost.
Frost dates: NOAA U.S. Climate Normals 1991–2020, station Missoula 2 Ne, MT (USC00245735), 3.5 km (2.2 mi) from the city center, elevation 1042 m, based on 22 years of records. Hardiness zone: USDA Plant Hardiness Zone Map 2023 for the ZIP code nearest to the city center. Microclimates (valleys, hills, cities, coasts) can be warmer or colder: check the local forecast before planting. How we calculate the data.