Weather in Boise, Idaho for September 2025
Until now, September 2025 in Boise has been nearly identical to the historical average, with a temperature of 29 °F (showing only a slight deviation of 0.4 °F).
Expect cooler weather in the next days in Boise with the forecast suggesting a temperature of 25.4 °F, lower than the historical average.
In general, the average temperature in Boise at the beginning of September is 32 °F. As the month progressed, temperatures tended to significantly cool down, reaching an average of 22.9 °F by the end of September.
With an average of 5 rainy days, Boise experiences minimal rainfall in September.
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Boise Weather September
Temperatures trend during September in Boise
September weather in Boise day by day
| Date | Weather | Temperatures | Rain | UV | More |
|---|---|---|---|---|---|
| Sept. 1 |  Sunny | 35° /18° | 0 mm | 9 | |
| Sept. 2 |  Patchy rain possible | 33° /20° | 0.2 mm | 8 | |
| Sept. 3 | Patchy rain possible | 30° /18° | 0.1 mm | 7 | |
| Sept. 4 | Sunny | 31° /17° | 0 mm | 7 | |
| Sept. 5 | Sunny | 32° /19° | 0 mm | 8 | |
| Sept. 6 |  Overcast | 32° /18° | 0 mm | 7 | |
| Sept. 7 |  Partly cloudy | 31° /18° | 0 mm | 7 | |
| Sept. 8 | Patchy rain possible | 31° /18° | 0.6 mm | 8 | |
| Sept. 9 | Sunny | 28° /17° | 0 mm | 7 | |
| Sept. 10 | Overcast | 27° /16° | 2.6 mm | 6 | |
| Sept. 11 |  Patchy light rain with thunder | 24° /13° | 1.1 mm | 6 | |
| Sept. 12 | Patchy rain possible | 19° /12° | 1.5 mm | 5 | |
| Sept. 13 | Sunny | 23° /13° | 0 mm | 7 | |
| Sept. 14 |  Cloudy | 25° /15° | 0 mm | 6 | |
| Sept. 15 | Cloudy | 24° /13° | 0 mm | 6 | |
| Sept. 16 | Sunny | 28° /10° | 0 mm | 1.4 | |
| Sept. 17 | Sunny | 29° /12° | 0 mm | 1.5 | |
| Sept. 18 | Sunny | 30° /15° | 0 mm | 1.5 | |
| Sept. 19 | Partly cloudy | 30° /20° | 0 mm | 1.1 | |
| Sept. 20 | Sunny | 24° /15° | 0 mm | 0 | |
| Sept. 21 | Sunny | 23° /16° | 0 mm | 5 | |
| Sept. 22 | Sunny | 25° /14° | 0 mm | 5 | |
| Sept. 23 | Sunny | 28° /17° | 0 mm | 6 | |
| Sept. 24 | Sunny | 26° /16° | 0 mm | 6 | |
| Sept. 25 | Sunny | 28° /16° | 0 mm | 6 | |
| Sept. 26 | Patchy rain possible | 31° /17° | 0.1 mm | 5 | |
| Sept. 27 | Patchy rain possible | 18° /11° | 0.6 mm | 3 | |
| Sept. 28 | Sunny | 18° /9° | 0 mm | 4 | |
| Sept. 29 | Sunny | 18° /8° | 0 mm | 4 | |
| Sept. 30 | Sunny | 21° /7° | 0 mm | 6 | |
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Boise in September - FAQ
September rainfall patterns in Boise
UV exposure in Boise during September
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Where is Boise?Get accurate weather forecasts for Boise, located at latitude 43.614 and longitude -116.203. Stay updated with localized weather information tailored for Boise.