Climate averages 1991–2020
Bismarck weather
in September.
A mild, moderately wet month: the 4th warmest and the joint 7th driest of the year. Meets the pleasant-weather rule
Long-term climate patterns, not a forecast for a particular trip.
September is a mild month in Bismarck: daytime highs average 21.4°C and nights cool to about 10.9°C. By daytime temperature it is the 4th warmest of the 12 months.
Expect about 46 mm of rain on roughly 7 days, which makes September a moderately wet month (the joint 7th 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 Fargo (304 km away). In September its highs average 20.9°C, 0.6°C cooler than Bismarck, with 72 mm of rain.
Among the 498 cities listed in the United States, Bismarck ranks joint 473rd of 498 for the warmest September highs and joint 171st of 498 for the driest September (rainfall, lowest first). The mean September high of those 498 cities is 26.9°C; Bismarck is 5.5°C cooler than that mean.
From September to October, average highs fall by 8.8°C to 12.7°C, and monthly rainfall falls from 46 mm to 45 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
Bismarck climate table
| Month | Average highHigh / low | Average low | Precipitation mm/month | Wet days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | -5.9°C-15.1°C | -15.1°C | 16 | 4.5 | 9.09 h |
| February | -2.9°C-12.5°C | -12.5°C | 18 | 4.5 | 10.310 h |
| March | 3.8°C-6.6°C | -6.6°C | 26 | 5.0 | 11.912 h |
| April | 11.4°C-0.1°C | -0.1°C | 46 | 7.5 | 13.614 h |
| May | 18.4°C7.3°C | 7.3°C | 73 | 9.8 | 15.015 h |
| June | 23.6°C13.3°C | 13.3°C | 96 | 10.9 | 15.816 h |
| July | 27.3°C16.7°C | 16.7°C | 77 | 9.7 | 15.515 h |
| August | 26.9°C15.9°C | 15.9°C | 58 | 7.4 | 14.214 h |
| September, selected | 21.4°C10.9°C | 10.9°C | 46 | 6.5 | 12.613 h |
| October | 12.7°C3.3°C | 3.3°C | 45 | 6.5 | 10.911 h |
| November | 3.6°C-4.6°C | -4.6°C | 21 | 4.1 | 9.49 h |
| December | -3.4°C-11.4°C | -11.4°C | 18 | 4.4 | 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
- Fargo in SeptemberUnited States · 304 kmHigh 20.9°C · Low 11.4°C · 72 mm rain
- Rapid City in SeptemberUnited States · 358 kmHigh 23.3°C · Low 11.2°C · 42 mm rain
- Winnipeg in SeptemberCanada · 435 kmHigh 18.5°C · Low 9.4°C · 68 mm rain
- Sioux Falls in SeptemberUnited States · 482 kmHigh 22.6°C · Low 12.8°C · 80 mm rain
- Regina in SeptemberCanada · 493 kmHigh 18.3°C · Low 8.2°C · 40 mm rain
- Sioux City in SeptemberUnited States · 591 kmHigh 23.8°C · Low 13.8°C · 75 mm rain
- Plymouth, United States in SeptemberUnited States · 601 kmHigh 21.5°C · Low 13.3°C · 82 mm rain
- Billings in SeptemberUnited States · 603 kmHigh 23.7°C · Low 10.4°C · 35 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 Bismarck) is explained once on the Bismarck year overview and on the Sources, method and limits page.