When is the last frost in Twin Bridges, MT?

For ZIP code 59754, the average last spring frost (32°F) is June 8, based on NOAA 1991-2020 climate normals for the Twin Bridges, MT weather station. There is a 1-in-10 chance of a frost after July 1.

When is the first frost in Twin Bridges, MT?

The average first fall frost (32°F) is September 2. There is a 1-in-10 chance of frost by August 16, so tender plants are at risk from that point on.

How long is the growing season in 59754?

In half of years, the frost-free season (between the last and first 32°F frost) is at least 82 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 59754Twin Bridges, MT

The average last spring frost in Twin Bridges is June 8 and the average first fall frost is September 2, giving a typical growing season of about 82 days. Dates are based on NOAA 1991-2020 climate normals.

Average last spring frost: Jun 8
Average first fall frost: Sep 2
Growing season: 82 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)	—	—	46 days	100%
Frost / freeze (32°F)	May 22 · Jun 8 · Jul 1	Aug 16 · Sep 2 · Sep 15	82 days	100%
Hard freeze (28°F)	May 7 · May 20 · Jun 6	Aug 31 · Sep 15 · Oct 1	116 days	100%

Where these dates come from

ZIP code 59754 is matched to the NOAA station Twin Bridges, MT, 2.6 km away, at 4,625 ft elevation (24 ft lower than the ZIP code's center). Nearby stations for comparison:

Station	Elevation	Avg last frost	Avg first frost
Twin Bridges, MT (used)	4,625 ft	Jun 8	Sep 2
Laurin 2Ne, MT	5,198 ft	May 24	Sep 22
Glen 4 N, MT	5,054 ft	—	—
Dillon Ap, MT	5,200 ft	Jun 2	Sep 13

Frost dates near Twin Bridges

Sheridan, MT 59749 · last May 24, first Sep 22
Silver Star, MT 59751 · last Jun 8, first Sep 2
Glen, MT 59732 · last —, first —
Melrose, MT 59743 · last Jun 10, first Sep 7
Pony, MT 59747 · last Jun 4, first Sep 18
Dillon, MT 59725 · last Jun 5, first Sep 13
Virginia City, MT 59755 · last Jun 4, first Sep 18
Whitehall, MT 59759 · last Jun 8, first Sep 2

Frequently asked questions

When is the last frost in Twin Bridges, MT?: For ZIP code 59754, the average last spring frost (32°F) is June 8, based on NOAA 1991-2020 climate normals for the Twin Bridges, MT weather station. There is a 1-in-10 chance of a frost after July 1.
When is the first frost in Twin Bridges, MT?: The average first fall frost (32°F) is September 2. There is a 1-in-10 chance of frost by August 16, so tender plants are at risk from that point on.
How long is the growing season in 59754?: In half of years, the frost-free season (between the last and first 32°F frost) is at least 82 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.