Climate change in Jefferson County, Montana
Since 1979, Jefferson County, Montana has warmed 2.6°F, with 2 more days above 90°F, about the same number of nights above 70°F and 12% less precipitation a year. Its climate in 1996–2025 is most like Sweet Grass County, MT's was in 1951–1980.
- Average temperature: +2.6°F
- Summer highs (Jun–Aug): +4.2°F
- Winter lows (Dec–Feb): +2.3°F
- Precipitation: −12%
- Wettest day of the year: −26%
- Longest dry spell: +4 days
- Days above 90°F: +2 days
- Nights above 70°F: +0 days
- Freezing nights: −8 days
- Frost-free season: +14 days
- Muggy days: +0 days
- Summer heat index (Jun–Aug): +4.0°F
- Extreme fire-weather days: +17 days
Changes follow the trend line through every year from 1979 to 2025. Data: NOAA nClimGrid-Daily; humidity from gridMET, adjusted to airport observations.