Bozeman, MT planting zone & frost dates

Bozeman is in USDA hardiness zone 5a. The last spring frost usually comes around May 26 and the first fall frost around September 22, for a growing season of about 116 days.

USDA hardiness zone5aavg. extreme winter low -20°F to -15°F

Average last spring frostMay 2690% chance of no frost after June 14

Average first fall frostSeptember 2210% chance of frost by September 5

Growing season116 daysfrost-free days in an average year

Planting calendar for Bozeman

Dates are counted from the average last spring frost (May 26) 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 31 – Apr 14 Transplant outdoors: Jun 2 – Jun 9
Peppers	Start seeds indoors: Mar 17 – Mar 31 Transplant outdoors: Jun 9 – Jun 16
Eggplant	Start seeds indoors: Mar 17 – Mar 31 Transplant outdoors: Jun 9 – Jun 16
Broccoli	Start seeds indoors: Mar 17 – Mar 31 Transplant outdoors: Apr 28 – May 12
Cabbage	Start seeds indoors: Mar 17 – Mar 31 Transplant outdoors: Apr 28 – May 12
Onions (sets)	Plant outdoors: Apr 28 – May 12
Peas	Sow outdoors: Apr 14 – Apr 28
Spinach	Sow outdoors: Apr 14 – Apr 28
Lettuce	Sow outdoors: Apr 28 – May 12
Carrots	Sow outdoors: Apr 28 – May 12
Potatoes	Plant outdoors: Apr 28 – May 12
Beans	Sow outdoors: Jun 2 – Jun 9
Sweet corn	Sow outdoors: Jun 2 – Jun 9
Cucumbers	Sow outdoors: Jun 2 – Jun 9
Squash & zucchini	Sow outdoors: Jun 2 – Jun 9
Basil	Start seeds indoors: Apr 14 – Apr 28 Transplant outdoors: Jun 2 – Jun 9

Fall garden: cool-season crops like lettuce, spinach and kale can be sown again around Jul 28 (8 weeks before the average first fall frost on Sep 22).

Frost risk in detail

	90% chance	50% chance	10% chance
Last 32°F frost in spring is after	May 9	May 26	Jun 14
First 32°F frost in fall is before	Oct 5	Sep 22	Sep 5

How to read it: in spring there is a 10% chance of a frost after June 14, so that is a safe date for tender plants. In fall there is a 10% chance of frost before September 5. A hard freeze (28°F) usually ends around May 8.

Hardiness zone by ZIP code in Bozeman

59715 zone 5a
59718 zone 5a
59719 zone 5a
59771 zone 5a
59772 zone 5a

Nearby cities

Helena zone 5a, last frost May 9
Butte zone 4b, last frost Jun 13
Great Falls zone 4b, last frost May 6
Billings zone 5a, last frost May 10
Missoula zone 5b, last frost May 10
Kalispell zone 5b, last frost May 31

All cities in Montana → · Other zone 5a cities →

Questions

What growing zone is Bozeman, MT?

Bozeman is in USDA Plant Hardiness Zone 5a (average extreme winter low -20°F to -15°F), according to the USDA 2023 map.

When is the last frost in Bozeman?

The average last spring frost (32°F) in Bozeman is May 26. There is still a 10% chance of frost until June 14.

When can I plant tomatoes in Bozeman?

Transplant tomatoes outdoors 1–2 weeks after the average last frost: around Jun 2 – Jun 9. Start seeds indoors 6–8 weeks before the last frost.

Frost dates: NOAA U.S. Climate Normals 1991–2020, station Bozeman Montana State Univ, MT (USC00241044), 2.0 km (1.2 mi) from the city center, elevation 1498 m, based on 30 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.