Climate averages 1991–2020
Naperville weather
in September.
A warm, 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 warm month in Naperville: daytime highs average 23.1°C and nights cool to about 14.3°C. By daytime temperature it is the 4th warmest of the 12 months.
Expect about 77 mm of rain on roughly 8 days, which makes September a moderately wet month (the 6th driest of the 12 months). Daylight, from sunrise to sunset, lasts about 12 h 31 min on an average September day.
The nearest other city in this atlas is Bolingbrook (12 km away). In September its highs average 23.2°C, about as warm as Naperville, with 74 mm of rain.
Among the 498 cities listed in the United States, Naperville ranks joint 401st of 498 for the warmest September highs and joint 259th of 498 for the driest September (rainfall, lowest first). The mean September high of those 498 cities is 26.9°C; Naperville is 3.8°C cooler than that mean.
From September to October, average highs fall by 6.9°C to 16.2°C, and monthly rainfall rises from 77 mm to 80 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
Naperville climate table
| Month | Average highHigh / low | Average low | Precipitation mm/month | Wet days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | -0.8°C-8.6°C | -8.6°C | 54 | 8.1 | 9.510 h |
| February | 1.7°C-7.1°C | -7.1°C | 50 | 7.1 | 10.611 h |
| March | 7.8°C-1.6°C | -1.6°C | 68 | 9.6 | 11.912 h |
| April | 14.4°C4.2°C | 4.2°C | 113 | 11.8 | 13.313 h |
| May | 20.4°C10.5°C | 10.5°C | 117 | 12.7 | 14.515 h |
| June | 25.6°C16.2°C | 16.2°C | 108 | 11.7 | 15.215 h |
| July | 27.8°C18.9°C | 18.9°C | 94 | 11.2 | 14.915 h |
| August | 26.8°C18.2°C | 18.2°C | 92 | 10.5 | 13.914 h |
| September, selected | 23.1°C14.3°C | 14.3°C | 77 | 8.3 | 12.513 h |
| October | 16.2°C7.9°C | 7.9°C | 80 | 9.1 | 11.111 h |
| November | 8.5°C1.0°C | 1.0°C | 64 | 8.1 | 9.910 h |
| December | 2.1°C-4.9°C | -4.9°C | 55 | 8.0 | 9.29 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
- Bolingbrook in SeptemberUnited States · 12 kmHigh 23.2°C · Low 14.3°C · 74 mm rain
- Aurora (Illinois), United States in SeptemberUnited States · 15 kmHigh 23.2°C · Low 14.1°C · 77 mm rain
- Schaumburg in SeptemberUnited States · 28 kmHigh 22.9°C · Low 14.2°C · 75 mm rain
- Joliet in SeptemberUnited States · 29 kmHigh 23.8°C · Low 14.5°C · 75 mm rain
- Elgin in SeptemberUnited States · 30 kmHigh 23.1°C · Low 14.3°C · 78 mm rain
- Cicero in SeptemberUnited States · 33 kmHigh 23.1°C · Low 15.2°C · 75 mm rain
- Arlington Heights in SeptemberUnited States · 36 kmHigh 22.7°C · Low 15.1°C · 75 mm rain
- Chicago in SeptemberUnited States · 42 kmHigh 22.7°C · Low 15.8°C · 75 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 Naperville) is explained once on the Naperville year overview and on the Sources, method and limits page.
Aurora (Illinois), United States lies in the same rainfall cell, so its rainfall figures are identical to these; temperatures differ because they come from smaller 0.1° cells.