When is the last frost in Butte, MT?

For ZIP code 59703, the average last spring frost (32°F) is June 13, based on NOAA 1991-2020 climate normals for the Butte Bert Mooney Ap, MT weather station. There is a 1-in-10 chance of a frost after July 1.

When is the first frost in Butte, MT?

The average first fall frost (32°F) is September 5. There is a 1-in-10 chance of frost by August 24, so tender plants are at risk from that point on.

How long is the growing season in 59703?

In half of years, the frost-free season (between the last and first 32°F frost) is at least 83 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.

Frost dates for 59703Butte, MT

The average last spring frost in Butte is June 13 and the average first fall frost is September 5, giving a typical growing season of about 83 days. Dates are based on NOAA 1991-2020 climate normals.

Average last spring frost: Jun 13
Average first fall frost: Sep 5
Growing season: 83 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.

Spring dates: chance of a frost AFTER the date. Fall dates: chance of a frost BEFORE the date.
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)	—	—	49 days	100%
Frost / freeze (32°F)	May 27 · Jun 13 · Jul 1	Aug 24 · Sep 5 · Sep 19	83 days	100%
Hard freeze (28°F)	May 8 · May 21 · Jun 10	Sep 2 · Sep 17 · Oct 1	117 days	100%

Where these dates come from

ZIP code 59703 is matched to the NOAA station Butte Bert Mooney Ap, MT, 12.5 km away, at 5,506 ft elevation (482 ft lower than the ZIP code's center). Nearby stations for comparison:

Station	Elevation	Avg last frost	Avg first frost
Butte Bert Mooney Ap, MT (used)	5,506 ft	Jun 13	Sep 5
Divide, MT	5,350 ft	Jun 10	Sep 7
Wise Rvr 3 Wnw, MT	5,730 ft	—	—
Anaconda, MT	5,230 ft	Jun 1	Sep 14

Frost dates near Butte

Butte, MT 59702 · last Jun 13, first Sep 5
Ramsay, MT 59748 · last Jun 13, first Sep 5
Divide, MT 59727 · last —, first —
Melrose, MT 59743 · last Jun 10, first Sep 7
Warm Springs, MT 59756 · last —, first —
Wise River, MT 59762 · last —, first —
Anaconda, MT 59711 · last Jun 1, first Sep 14
Silver Star, MT 59751 · last Jun 8, first Sep 2

Frequently asked questions

When is the last frost in Butte, MT?: For ZIP code 59703, the average last spring frost (32°F) is June 13, based on NOAA 1991-2020 climate normals for the Butte Bert Mooney Ap, MT weather station. There is a 1-in-10 chance of a frost after July 1.
When is the first frost in Butte, MT?: The average first fall frost (32°F) is September 5. There is a 1-in-10 chance of frost by August 24, so tender plants are at risk from that point on.
How long is the growing season in 59703?: In half of years, the frost-free season (between the last and first 32°F frost) is at least 83 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.