St. Mary, MT Weather & Growing Conditions
Overnight
27°F
Mostly Cloudy
Mostly cloudy, with a low around 27. South wind around 6 mph.
7-day forecast
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Overnight | 27°F | Mostly Cloudy | 6 mph S | 0% |
| Wednesday | 47°F | Sunny | 2 to 6 mph SW | 0% |
| Wednesday Night | 29°F | Mostly Clear | 7 to 21 mph SW | 0% |
| Thursday | 39°F | Partly Sunny then Slight Chance Light Snow | 21 mph WSW | 16% |
| Thursday Night | 30°F | Slight Chance Light Snow then Mostly Cloudy | 20 to 30 mph WSW | 16% |
| Friday | 40°F | Partly Sunny | 25 to 30 mph WSW | 11% |
| Friday Night | 33°F | Mostly Cloudy | 21 to 35 mph WSW | 11% |
| Saturday | 47°F | Partly Sunny | 12 to 21 mph SW | 10% |
| Saturday Night | 37°F | Partly Cloudy then Slight Chance Light Rain | 12 to 25 mph SW | 15% |
| Sunday | 49°F | Chance Light Rain | 18 to 25 mph WSW | 30% |
| Sunday Night | 33°F | Chance Rain And Snow | 13 to 28 mph WSW | 30% |
| Monday | 45°F | Partly Sunny | 8 to 13 mph WSW | 4% |
| Monday Night | 33°F | Slight Chance Rain And Snow | 8 to 22 mph WSW | 15% |
| Tuesday | 47°F | Slight Chance Light Rain | 16 to 22 mph WSW | 24% |
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 Nov 4, 2026.