Jefferson County, Montana · Frost dates
Jefferson County frost dates.
First-frost, last-frost, and growing-season length for Jefferson County, Montana. Sourced from NOAA 1991-2020 Climate Normals.
Data confidence: high · USDA zone: 4b
32°F — light freeze
Last spring frost
- 10%
- 06-25
- 20%
- 06-19
- 50%
- 06-07
- 80%
- 05-29
- 90%
- 05-24
First fall frost
- 10%
- 08-25
- 20%
- 08-30
- 50%
- 09-08
- 80%
- 09-17
- 90%
- 09-21
28°F — killing freeze
Last spring freeze
- 10%
- 06-05
- 20%
- 05-31
- 50%
- 05-21
- 80%
- 05-11
- 90%
- 05-07
First fall freeze
- 10%
- 09-06
- 20%
- 09-11
- 50%
- 09-21
- 80%
- 09-30
- 90%
- 10-03
Growing season length (days, 28°F threshold)
- Short year
- 93
- Median
- 123
- Long year
- 149
Source NOAA station
BOULDER, MT US
7.8 mi · 30 yrs of record (1991–2020) · 4904 ft elev.
Data from BOULDER, MT US, 7.8 miles away with 30-year NOAA record (1991-2020).
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