Weather in Yellowstone County, Montana for September 2026
Red Flag Warning - See hour by hour.
Until now, September 2026 in Yellowstone County has been nearly identical to the historical average, with a temperature of 30.8 °F (showing only a slight deviation of 0.3 °F).
The forecast for the next days in Yellowstone County predicts a temperature of 23.8 °F, which is cooler than the historical average.
In general, the average temperature in Yellowstone County at the beginning of September is 30.4 °F. As the month progressed, temperatures tended to noticeably cool down, reaching an average of 27.9 °F by the end of September.
Yellowstone County experiences moderate rainfall in September, with an average of 7 rainy days and a total precipitation of 90.7 mm.
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Yellowstone County Weather September
Temperatures trend during September in Yellowstone County
September weather in Yellowstone County day by day
| Date | Weather | Temperatures | Rain | UV | More |
|---|---|---|---|---|---|
| Sept. 1 |  Sunny | 32° /12° | 0.2 mm | 6 | |
| Sept. 2 | Sunny | 35° /15° | 0 mm | 8 | |
| Sept. 3 |  Overcast | 30° /15° | 0.1 mm | 6 | |
| Sept. 4 |  Cloudy | 29° /13° | 0 mm | 6 | |
| Sept. 5 | Sunny | 27° /10° | 0 mm | 7 | |
| Sept. 6 | Sunny | 30° /10° | 0.1 mm | 7 | |
| Sept. 7 | Sunny | 30° /12° | 0 mm | 7 | |
| Sept. 8 | Sunny | 31° /13° | 0.2 mm | 8 | |
| Sept. 9 |  Partly cloudy | 30° /13° | 0 mm | 8 | |
| Sept. 10 | Sunny | 32° /13° | 0 mm | 6.4 | |
| Sept. 11 | Sunny | 18° /12° | 0.1 mm | 5.3 | |
| Sept. 12 | Overcast | 20° /11° | 0 mm | 3.6 | |
| Sept. 13 | Overcast | 17° /10° | 1 mm | 4.7 | |
| Sept. 14 | Overcast | 20° /7° | 0 mm | 5 | |
| Sept. 15 | Overcast | 20° /8° | 0 mm | 5 | |
| Sept. 16 | Overcast | 18° /9° | 0 mm | 4 | |
| Sept. 17 | Sunny | 24° /7° | 0 mm | 6 | |
| Sept. 18 | Sunny | 27° /11° | 0 mm | 7 | |
| Sept. 19 | Sunny | 33° /15° | 0 mm | 8 | |
| Sept. 20 | Overcast | 27° /19° | 0 mm | 6 | |
| Sept. 21 | Sunny | 31° /16° | 0 mm | 8 | |
| Sept. 22 | Sunny | 23° /14° | 0 mm | 6 | |
| Sept. 23 | Overcast | 24° /7° | 0 mm | 6 | |
| Sept. 24 | Sunny | 27° /8° | 0 mm | 7 | |
| Sept. 25 | Sunny | 31° /11° | 0 mm | 8 | |
| Sept. 26 | Sunny | 27° /13° | 0 mm | 7 | |
| Sept. 27 | Sunny | 28° /7° | 0 mm | 7 | |
| Sept. 28 | Sunny | 29° /9° | 0 mm | 7 | |
| Sept. 29 | Sunny | 31° /11° | 0 mm | 8 | |
| Sept. 30 | Sunny | 22° /8° | 0 mm | 6 | |
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Yellowstone County in September - FAQ
What are the expected maximum and minimum temperatures in Yellowstone County during September?
How much rainfall should be expected in Yellowstone County during September?
What are the typical wind conditions in Yellowstone County during September?
UV exposure in Yellowstone County during September
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Where is Yellowstone County?Get accurate weather forecasts for Yellowstone County, located at latitude 45.783 and longitude -108.501. Stay updated with localized weather information tailored for Yellowstone County.