St. Mary, MT Weather & Growing Conditions
Overnight
44°F
Mostly Cloudy
Mostly cloudy, with a low around 44. Northeast wind around 1 mph.
7-day forecast
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Overnight | 44°F | Mostly Cloudy | 1 mph NE | 1% |
| Saturday | 64°F | Sunny | 1 to 7 mph E | 3% |
| Saturday Night | 43°F | Mostly Clear | 3 to 7 mph SSW | 0% |
| Sunday | 66°F | Sunny | 7 mph WSW | 0% |
| Sunday Night | 44°F | Mostly Clear | 5 to 8 mph WSW | 0% |
| Monday | 66°F | Sunny | 10 mph WSW | 0% |
| Monday Night | 45°F | Mostly Clear | 10 mph WSW | 0% |
| Tuesday | 65°F | Sunny | 8 mph WSW | 0% |
| Tuesday Night | 45°F | Partly Cloudy | 6 mph SW | 0% |
| Wednesday | 65°F | Mostly Sunny | 6 to 13 mph SW | 0% |
| Wednesday Night | 45°F | Partly Cloudy | 9 mph SW | 1% |
| Thursday | 64°F | Mostly Sunny | 8 mph SW | 1% |
| Thursday Night | 45°F | Partly Cloudy | 6 mph SW | 8% |
| Friday | 61°F | Partly Sunny then Slight Chance Light Rain | 7 mph SW | 16% |
Forecast source: National Weather Service (api.weather.gov). Updated through the day.
Growing snapshot for St. Mary, MT
Last spring frost
Jun 3
First fall frost
Sep 8
Growing season
94 days
Hardiness zone
4b
Explore more for St. Mary, MT: full frost dates · planting calendar · Montana frost dates
Climate data from the nearest NOAA station, St. Mary 1 Ssw, Mt (4.5 mi). Frost dates are 1991–2020 averages, not a forecast. Page updated Sep 19, 2026.