Climate averages 1991–2020
Green Bay weather
in September.
A mild, moderately wet month: the 4th warmest and the 6th driest of the year.
Long-term climate patterns, not a forecast for a particular trip.
September is a mild month in Green Bay: daytime highs average 21.5°C and nights cool to about 13.3°C. By daytime temperature it is the 4th warmest of the 12 months.
Expect about 67 mm of rain on roughly 9 days, which makes September a moderately wet month (the 6th driest of the 12 months). Daylight, from sunrise to sunset, lasts about 12 h 34 min on an average September day.
The nearest other city in this atlas is Appleton (42 km away). In September its highs average 21.2°C, about as warm as Green Bay, with 72 mm of rain.
Among the 498 cities listed in the United States, Green Bay ranks joint 470th of 498 for the warmest September highs and joint 193rd of 498 for the driest September (rainfall, lowest first). The mean September high of those 498 cities is 26.9°C; Green Bay is 5.4°C cooler than that mean.
From September to October, average highs fall by 7.5°C to 14.0°C, and monthly rainfall rises from 67 mm to 71 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
Green Bay climate table
| Month | Average highHigh / low | Average low | Precipitation mm/month | Wet days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | -4.1°C-11.9°C | -11.9°C | 37 | 7.6 | 9.29 h |
| February | -2.3°C-10.8°C | -10.8°C | 33 | 6.5 | 10.410 h |
| March | 4.2°C-5.1°C | -5.1°C | 56 | 8.3 | 11.912 h |
| April | 11.3°C1.6°C | 1.6°C | 80 | 11.4 | 13.413 h |
| May | 18.5°C8.7°C | 8.7°C | 86 | 11.4 | 14.815 h |
| June | 24.1°C14.9°C | 14.9°C | 91 | 11.2 | 15.515 h |
| July | 26.7°C17.8°C | 17.8°C | 88 | 11.2 | 15.215 h |
| August | 25.6°C17.3°C | 17.3°C | 87 | 10.4 | 14.014 h |
| September, selected | 21.5°C13.3°C | 13.3°C | 67 | 9.1 | 12.613 h |
| October | 14.0°C6.6°C | 6.6°C | 71 | 9.5 | 11.011 h |
| November | 6.1°C-0.4°C | -0.4°C | 54 | 8.2 | 9.610 h |
| December | -0.6°C-7.2°C | -7.2°C | 45 | 7.3 | 8.99 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
- Appleton in SeptemberUnited States · 42 kmHigh 21.2°C · Low 13.0°C · 72 mm rain
- Milwaukee in SeptemberUnited States · 165 kmHigh 20.8°C · Low 16.2°C · 76 mm rain
- Waukesha in SeptemberUnited States · 168 kmHigh 22.0°C · Low 14.2°C · 75 mm rain
- Madison in SeptemberUnited States · 195 kmHigh 22.1°C · Low 13.1°C · 84 mm rain
- Racine in SeptemberUnited States · 200 kmHigh 20.8°C · Low 17.0°C · 81 mm rain
- Kenosha in SeptemberUnited States · 216 kmHigh 21.0°C · Low 17.1°C · 80 mm rain
- Waukegan in SeptemberUnited States · 240 kmHigh 21.2°C · Low 17.1°C · 83 mm rain
- Grand Rapids in SeptemberUnited States · 256 kmHigh 22.1°C · Low 13.6°C · 79 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 Green Bay) is explained once on the Green Bay year overview and on the Sources, method and limits page.