Climate averages 1991–2020
Missoula weather
in September.
A warm, fairly dry month: the 3rd warmest and the 3rd driest of the year. Meets the pleasant-weather rule
Long-term climate patterns, not a forecast for a particular trip.
September is a warm month in Missoula: daytime highs average 22.5°C and nights cool to about 9.8°C. By daytime temperature it is the 3rd warmest of the 12 months.
Expect about 30 mm of rain on roughly 6 days, which makes September a fairly dry month (the 3rd driest of the 12 months). Daylight, from sunrise to sunset, lasts about 12 h 37 min on an average September day.
The nearest other city in this atlas is Spokane Valley (261 km away). In September its highs average 23.2°C, 0.7°C warmer than Missoula, with 22 mm of rain.
Among the 498 cities listed in the United States, Missoula ranks joint 433rd of 498 for the warmest September highs and joint 143rd of 498 for the driest September (rainfall, lowest first). The mean September high of those 498 cities is 26.9°C; Missoula is 4.4°C cooler than that mean.
From September to October, average highs fall by 8.9°C to 13.6°C, and monthly rainfall rises from 30 mm to 44 mm.
The annual picture
September in context
Monthly precipitation
Average total · mmAverages from hourly ERA5 reanalysis data. Actual weather varies from year to year. How these numbers are calculated
Every month, side by side
Missoula climate table
| Month | Average highHigh / low | Average low | Precipitation mm/month | Wet days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 0.6°C-6.9°C | -6.9°C | 45 | 10.8 | 9.09 h |
| February | 2.7°C-5.7°C | -5.7°C | 41 | 9.9 | 10.310 h |
| March | 7.0°C-1.7°C | -1.7°C | 44 | 11.0 | 11.912 h |
| April | 11.4°C1.5°C | 1.5°C | 53 | 11.4 | 13.614 h |
| May | 17.9°C6.3°C | 6.3°C | 56 | 11.0 | 15.015 h |
| June | 22.2°C10.4°C | 10.4°C | 56 | 10.0 | 15.816 h |
| July | 28.8°C15.3°C | 15.3°C | 19 | 4.6 | 15.515 h |
| August | 28.6°C14.9°C | 14.9°C | 19 | 3.8 | 14.214 h |
| September, selected | 22.5°C9.8°C | 9.8°C | 30 | 5.8 | 12.613 h |
| October | 13.6°C3.5°C | 3.5°C | 44 | 8.6 | 10.911 h |
| November | 5.2°C-2.3°C | -2.3°C | 50 | 10.0 | 9.49 h |
| December | -0.1°C-7.4°C | -7.4°C | 51 | 10.4 | 8.69 h |
Precipitation (rain or snow, as water) is the average of the 30 separate monthly totals. A wet day is a local calendar day with at least 1 mm of precipitation. Daylight is the calculated sunrise-to-sunset length, not measured sunshine.
Compare places
September in nearby cities
- Spokane Valley in SeptemberUnited States · 261 kmHigh 23.2°C · Low 10.5°C · 22 mm rain
- Spokane in SeptemberUnited States · 274 kmHigh 23.7°C · Low 11.0°C · 19 mm rain
- Lethbridge in SeptemberCanada · 326 kmHigh 19.7°C · Low 8.3°C · 37 mm rain
- Kennewick in SeptemberUnited States · 400 kmHigh 27.4°C · Low 13.9°C · 6.9 mm rain
- Boise in SeptemberUnited States · 401 kmHigh 26.2°C · Low 12.6°C · 10 mm rain
- Tri-Cities in SeptemberUnited States · 404 kmHigh 27.5°C · Low 14.0°C · 6.9 mm rain
- Meridian in SeptemberUnited States · 408 kmHigh 26.1°C · Low 12.4°C · 9.8 mm rain
- Nampa in SeptemberUnited States · 422 kmHigh 26.5°C · Low 13.4°C · 9.8 mm rain
Read the numbers correctly
Climate, not a promise.
These patterns help compare months. They cannot tell you the weather on a specific day of your trip.
Sources, method and limitsHow these numbers are made (what the highs, lows and rain days mean, the sources and the model cell used for Missoula) is explained once on the Missoula year overview and on the Sources, method and limits page.