Butte, MT planting zone & frost dates

Butte is in USDA hardiness zone 4b. The last spring frost usually comes around June 13 and the first fall frost around September 5, for a growing season of about 83 days.

USDA hardiness zone4bavg. extreme winter low -25°F to -20°F

Average last spring frostJune 1390% chance of no frost after July 1

Average first fall frostSeptember 510% chance of frost by August 24

Growing season83 daysfrost-free days in an average year

Planting calendar for Butte

Dates are counted from the average last spring frost (June 13) 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: Apr 18 – May 2 Transplant outdoors: Jun 20 – Jun 27
Peppers	Start seeds indoors: Apr 4 – Apr 18 Transplant outdoors: Jun 27 – Jul 4
Eggplant	Start seeds indoors: Apr 4 – Apr 18 Transplant outdoors: Jun 27 – Jul 4
Broccoli	Start seeds indoors: Apr 4 – Apr 18 Transplant outdoors: May 16 – May 30
Cabbage	Start seeds indoors: Apr 4 – Apr 18 Transplant outdoors: May 16 – May 30
Onions (sets)	Plant outdoors: May 16 – May 30
Peas	Sow outdoors: May 2 – May 16
Spinach	Sow outdoors: May 2 – May 16
Lettuce	Sow outdoors: May 16 – May 30
Carrots	Sow outdoors: May 16 – May 30
Potatoes	Plant outdoors: May 16 – May 30
Beans	Sow outdoors: Jun 20 – Jun 27
Sweet corn	Sow outdoors: Jun 20 – Jun 27
Cucumbers	Sow outdoors: Jun 20 – Jun 27
Squash & zucchini	Sow outdoors: Jun 20 – Jun 27
Basil	Start seeds indoors: May 2 – May 16 Transplant outdoors: Jun 20 – Jun 27

Fall garden: cool-season crops like lettuce, spinach and kale can be sown again around Jul 11 (8 weeks before the average first fall frost on Sep 5).

Frost risk in detail

	90% chance	50% chance	10% chance
Last 32°F frost in spring is after	May 27	Jun 13	Jul 1
First 32°F frost in fall is before	Sep 19	Sep 5	Aug 24

How to read it: in spring there is a 10% chance of a frost after July 1, so that is a safe date for tender plants. In fall there is a 10% chance of frost before August 24. A hard freeze (28°F) usually ends around May 21.

Hardiness zone by ZIP code in Butte

59701 zone 5a
59702 zone 4a
59703 zone 4a
59707 zone 4b
59750 zone 5a

Nearby cities

Helena zone 5a, last frost May 9
Bozeman zone 5a, last frost May 26
Missoula zone 5b, last frost May 10
Great Falls zone 4b, last frost May 6
Kalispell zone 5b, last frost May 31
Billings zone 5a, last frost May 10

All cities in Montana → · Other zone 4b cities →

Questions

What growing zone is Butte, MT?

Butte is in USDA Plant Hardiness Zone 4b (average extreme winter low -25°F to -20°F), according to the USDA 2023 map. Some ZIP codes of the city fall in zones 4a, 5a.

When is the last frost in Butte?

The average last spring frost (32°F) in Butte is June 13. There is still a 10% chance of frost until July 1.

When can I plant tomatoes in Butte?

Transplant tomatoes outdoors 1–2 weeks after the average last frost: around Jun 20 – Jun 27. Start seeds indoors 6–8 weeks before the last frost.

Frost dates: NOAA U.S. Climate Normals 1991–2020, station Butte Bert Mooney Ap, MT (USW00024135), 5.1 km (3.2 mi) from the city center, elevation 1678 m, based on 28 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.