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Arch Lake Weather Forecast
| TODAY | TONIGHT | SUNDAY | SUNDAY NIGHT | MONDAY | MONDAY NIGHT | TUESDAY | TUESDAY NIGHT | WEDNESDAY | WEDNESDAY NIGHT | THURSDAY | THURSDAY NIGHT |
 |  |  |  | |  | | | | |  |  |
| Mostly Sunny | Mostly Cloudy | Clouds | Rain/Snow Showers | Sunny | Mostly Clear | Sunny | Mostly Clear | Mostly Sunny | Mostly Clear | Rain Showers | Chance of Showers |
| Hi: 69°FHi: 21°C | Lo: 35°FLo: 2°C | Hi: 70°FHi: 21°C | Lo: 29°FLo: -2°C | Hi: 59°FHi: 15°C | Lo: 25°FLo: -4°C | Hi: 65°FHi: 18°C | Lo: 29°FLo: -2°C | Hi: 65°FHi: 18°C | Lo: 29°FLo: -2°C | Hi: 69°FHi: 21°C | Lo: 31°FLo: -1°C |
| POP: 20% | POP: 20% | POP: 20% |
POP = Probability of Precipitation.
Weather Outlook Updated: 350 AM MDT Sat Sep 12 2026 
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Issued: 104 AM MDT Sat Sep 12 2026
Key Messages
- Below average temperatures through the middle of next week.
- Occasional chances of showers (mainly light) through Monday. Scattered thunderstorms possible in southeast Montana Sunday evening, some possibly strong.
- Periods of overnight and morning low clouds and fog in the foothills through Sunday.
- Breezy west winds Monday; gusts over 50 mph possible near Big Timber and Harlowton.
Discussion
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Next 7 Days...
The forecast for Saturday remains roughly the same. High temperatures today will...