When is the last frost in Mc Allister, MT?

For ZIP code 59740, the average last spring frost (32°F) is June 16, based on NOAA 1991-2020 climate normals for the Ennis, MT weather station. There is a 1-in-10 chance of a frost after July 6.

When is the first frost in Mc Allister, MT?

The average first fall frost (32°F) is September 4. 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 59740?

In half of years, the frost-free season (between the last and first 32°F frost) is at least 78 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 59740Mc Allister, MT

The average last spring frost in Mc Allister is June 16 and the average first fall frost is September 4, giving a typical growing season of about 78 days. Dates are based on NOAA 1991-2020 climate normals.

Average last spring frost: Jun 16
Average first fall frost: Sep 4
Growing season: 78 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)	—	—	47 days	100%
Frost / freeze (32°F)	May 30 · Jun 16 · Jul 6	Aug 20 · Sep 4 · Sep 19	78 days	100%
Hard freeze (28°F)	May 9 · May 23 · Jun 12	Sep 1 · Sep 18 · Oct 2	114 days	100%

Where these dates come from

ZIP code 59740 is matched to the NOAA station Ennis, MT, 9.1 km away, at 4,953 ft elevation (368 ft lower than the ZIP code's center). Nearby stations for comparison:

Station	Elevation	Avg last frost	Avg first frost
Ennis, MT (used)	4,953 ft	Jun 16	Sep 4
Norris Madison Pwr House, MT	4,745 ft	Apr 30	Oct 10
Virginia City, MT	5,773 ft	Jun 4	Sep 18
Laurin 2Ne, MT	5,198 ft	May 24	Sep 22

Frost dates near Mc Allister

Ennis, MT 59729 · last Jun 16, first Sep 4
Norris, MT 59745 · last Apr 30, first Oct 10
Virginia City, MT 59755 · last Jun 4, first Sep 18
Pony, MT 59747 · last Jun 4, first Sep 18
Sheridan, MT 59749 · last May 24, first Sep 22
Cameron, MT 59720 · last Jun 4, first Sep 18
Alder, MT 59710 · last Jun 6, first Sep 14
Big Sky, MT 59716 · last —, first —

Frequently asked questions

When is the last frost in Mc Allister, MT?: For ZIP code 59740, the average last spring frost (32°F) is June 16, based on NOAA 1991-2020 climate normals for the Ennis, MT weather station. There is a 1-in-10 chance of a frost after July 6.
When is the first frost in Mc Allister, MT?: The average first fall frost (32°F) is September 4. 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 59740?: In half of years, the frost-free season (between the last and first 32°F frost) is at least 78 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.