St. Mary, MT Weather & Growing Conditions
Today
68°F
Mostly Sunny
Mostly sunny, with a high near 68. Southwest wind 2 to 7 mph.
7-day forecast
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Today | 68°F | Mostly Sunny | 2 to 7 mph SW | 1% |
| Tonight | 43°F | Mostly Clear | 8 mph WSW | 1% |
| Wednesday | 73°F | Sunny | 6 to 9 mph WSW | 0% |
| Wednesday Night | 48°F | Mostly Clear | 9 mph WSW | 0% |
| Thursday | 79°F | Sunny | 8 to 12 mph W | 0% |
| Thursday Night | 49°F | Mostly Clear | 3 to 10 mph WSW | 0% |
| Friday | 81°F | Sunny | 2 to 17 mph WSW | 0% |
| Friday Night | 51°F | Clear | 6 to 16 mph WSW | 0% |
| Saturday | 78°F | Sunny | 5 to 15 mph WSW | 0% |
| Saturday Night | 49°F | Mostly Clear | 5 to 13 mph W | 0% |
| Sunday | 75°F | Mostly Sunny | 2 to 8 mph SW | 2% |
| Sunday Night | 47°F | Partly Cloudy | 3 to 9 mph NE | 9% |
| Monday | 73°F | Mostly Sunny then Slight Chance Showers And Thunderstorms | 2 to 7 mph ESE | 19% |
| Monday Night | 46°F | Slight Chance Showers And Thunderstorms then Mostly Clear | 3 to 8 mph S | 15% |
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 Aug 4, 2026.