When is the last frost in Heart Butte, MT?

For ZIP code 59448, the average last spring frost (32°F) is June 8, based on NOAA 1991-2020 climate normals for the E Glacier, MT weather station. There is a 1-in-10 chance of a frost after July 1.

When is the first frost in Heart Butte, MT?

The average first fall frost (32°F) is September 5. There is a 1-in-10 chance of frost by August 20, so tender plants are at risk from that point on.

How long is the growing season in 59448?

In half of years, the frost-free season (between the last and first 32°F frost) is at least 88 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 59448Heart Butte, MT

The average last spring frost in Heart Butte is June 8 and the average first fall frost is September 5, giving a typical growing season of about 88 days. Dates are based on NOAA 1991-2020 climate normals.

Average last spring frost: Jun 8
Average first fall frost: Sep 5
Growing season: 88 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)	—	—	52 days	100%
Frost / freeze (32°F)	May 24 · Jun 8 · Jul 1	Aug 20 · Sep 5 · Sep 20	88 days	100%
Hard freeze (28°F)	May 7 · May 21 · Jun 7	Sep 4 · Sep 23 · Oct 5	122 days	100%

Where these dates come from

ZIP code 59448 is matched to the NOAA station E Glacier, MT, 33.7 km away, at 4,806 ft elevation (23 ft lower than the ZIP code's center). Nearby stations for comparison:

Station	Elevation	Avg last frost	Avg first frost
E Glacier, MT (used)	4,806 ft	Jun 8	Sep 5
Blackleaf, MT	4,235 ft	Jun 9	Sep 3
Valier, MT	3,807 ft	May 17	Sep 24
Cut Bank Muni Ap, MT	3,838 ft	May 24	Sep 15

Frost dates near Heart Butte

Dupuyer, MT 59432 · last Jun 9, first Sep 3
East Glacier Park, MT 59434 · last Jun 8, first Sep 5
Browning, MT 59417 · last Jun 8, first Sep 5
Valier, MT 59486 · last May 17, first Sep 24
Pendroy, MT 59467 · last Jun 9, first Sep 3
Bynum, MT 59419 · last May 28, first Sep 12
Cut Bank, MT 59427 · last May 24, first Sep 15
Essex, MT 59916 · last May 9, first Oct 1

Frequently asked questions

When is the last frost in Heart Butte, MT?: For ZIP code 59448, the average last spring frost (32°F) is June 8, based on NOAA 1991-2020 climate normals for the E Glacier, MT weather station. There is a 1-in-10 chance of a frost after July 1.
When is the first frost in Heart Butte, MT?: The average first fall frost (32°F) is September 5. There is a 1-in-10 chance of frost by August 20, so tender plants are at risk from that point on.
How long is the growing season in 59448?: In half of years, the frost-free season (between the last and first 32°F frost) is at least 88 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.