Plant By Frost

Montana

Frost dates for Malta, MT

At this NOAA station the last spring frost (32°F) usually comes by May 10 and the first fall frost around September 29, giving a growing season of about 139 days.

May 10average last spring frost
September 29average first fall frost
JanAprJulOctDec

Frost odds

1 year in 10 the last spring frost is later thanMay 22
Half of years the last spring frost is later thanMay 10
9 years in 10 the last spring frost is later thanApril 29
1 year in 10 the first fall frost is earlier thanSeptember 17
Half of years the first fall frost is earlier thanSeptember 29
9 years in 10 the first fall frost is earlier thanOctober 10

A hard freeze (28°F) usually ends by April 30 and returns around October 6.

A light frost (36°F, which can still nip tender plants) usually ends by May 19 and returns around September 20.

Station USC00245334, elevation 690 m. Based on 23 years of 1991 to 2020 records. A garden higher up, in a hollow or far from this station can freeze later in spring.

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Sources

  1. U.S. Annual/Seasonal Climate Normals, 1991 to 2020 (freeze probability dates by station), NOAA National Centers for Environmental Information, checked 1 November 2026
  2. Annual/Seasonal Normals 1991 to 2020 documentation, NOAA National Centers for Environmental Information, checked 1 November 2026
  3. 2024 Gazetteer Files, ZIP Code Tabulation Areas, US Census Bureau, checked 1 November 2026