Frost dates for Plentywood, MT
At this NOAA station the last spring frost (32°F) usually comes by May 25 and the first fall frost around September 14, giving a growing season of about 111 days.
May 25average last spring frost
September 14average first fall frost
JanAprJulOctDec
Frost odds
| 1 year in 10 the last spring frost is later than | June 8 |
| Half of years the last spring frost is later than | May 25 |
| 9 years in 10 the last spring frost is later than | May 13 |
| 1 year in 10 the first fall frost is earlier than | September 2 |
| Half of years the first fall frost is earlier than | September 14 |
| 9 years in 10 the first fall frost is earlier than | September 25 |
A hard freeze (28°F) usually ends by May 15 and returns around September 22.
A light frost (36°F, which can still nip tender plants) usually ends by June 6 and returns around September 4.
Station USC00246586, elevation 624 m. Based on 24 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
- U.S. Annual/Seasonal Climate Normals, 1991 to 2020 (freeze probability dates by station), NOAA National Centers for Environmental Information, checked 1 November 2026
- Annual/Seasonal Normals 1991 to 2020 documentation, NOAA National Centers for Environmental Information, checked 1 November 2026
- 2024 Gazetteer Files, ZIP Code Tabulation Areas, US Census Bureau, checked 1 November 2026