September Weather in Naperville, United States

Last updated: June 24, 2025

In Naperville, United States, the average temperature in September hovers around 20°C (68°F), providing a pleasant climate for outdoor activities. However, temperatures can vary significantly, with a minimum of 2°C (36°F) and a maximum of 34°C (93°F). Expect 95 mm (3.8 in) of precipitation spread over about 10 days, contributing to an average humidity of 80%. Embrace the diverse weather while enjoying all that Naperville has to offer!

September Temperature in Naperville

In September in Naperville, the average temperature is 20°C (68°F), with maximums reaching up to 34°C (93°F) and minimums dropping as low as 2°C (36°F). This diverse range of temperatures makes Naperville an ideal destination for travelers seeking both warm days and cool evenings.

September Weather in Naperville: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in Naperville, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Naperville, September typically has an average temperature of 20°C (68°F), with highs reaching up to 34°C (93°F) and lows dropping to around 2°C (36°F).
JanFebMarAprMayJunJulAugSepOctNovDec252739486172757367543933
Data source: Temperature data for Naperville generated using information from the Copernicus Climate Change Service.
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The average of daily temperatures (24 hours) calculated across all days in the month.

September Precipitation in Naperville

In Naperville in September, the precipitation amount is 95 mm (3.8 in) over the course of 10 days.

September Precipitation Trends in Naperville

The chart displays monthly precipitation patterns in Naperville, with values for each month alongside September’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how September’s conditions compare to those of other months. In Naperville, September typically receives around 95 mm (3.8 inches) of precipitation spread over approximately 10 days.
JanFebMarAprMayJunJulAugSepOctNovDec63638711715715211991951295753
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Naperville

In Naperville in September, humidity is 80%. With an average temperature of 20°C (68°F), this humidity feels like traveling through a warm, dense blanket that clings to your skin, making you feel both sticky and lethargic as you explore the sights.

September Average Humidity in Naperville

This chart illustrates the average monthly humidity levels in Naperville, with September’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In September, average humidity in Naperville is approximately 80%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec82%83%84%85%79%82%80%81%80%82%88%84%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Naperville

In Naperville in September, the maximum UV index is 8, which corresponds to a very high Exposure Category. This means that the time to burn is only 15 minutes. For more detailed information, you can refer to the Hourly UV Index in Naperville.

Maximum UV Index Levels in Naperville for September

The chart shows the monthly maximum UV Index (UVI) for Naperville in September, representing the highest UV radiation level. The UVI measures the intensity of ultraviolet radiation from the sun, indicating the potential risk of sunburn and UV-related health issues. In September, the maximum UV index in Naperville typically reaches 8, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec34689101098642
Data source: Naperville September UVI data generated using information from the Copernicus Climate Change Service.

UV Risk Categories

  •  Extreme (11+): Avoid the sun, stay in shade.
  •  Very High (8-10): Limit sun exposure.
  •  High (6-7): Use SPF 30+ and protective clothing.
  •  Moderate (3-5): Midday shade recommended.
  •  Low (0-2): No protection needed.

How September Weather in Naperville Compares to Other Months

Weather in Naperville varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in Naperville, focusing on differences in temperature, rainfall, humidity, and UV levels.

This table compares monthly weather conditions in Naperville, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-4°C (26°F)62 mm (2.5 inches)82%moderate
February Weather-3°C (28°F)63 mm (2.5 inches)83%moderate
March Weather4°C (40°F)87 mm (3.4 inches)84%high
April Weather9°C (49°F)117 mm (4.6 inches)85%very high
May Weather16°C (61°F)157 mm (6.2 inches)79%very high
June Weather22°C (72°F)152 mm (6.0 inches)82%very high
July Weather24°C (76°F)119 mm (4.7 inches)80%very high
August Weather23°C (73°F)91 mm (3.6 inches)81%very high
September Weather20°C (68°F)95 mm (3.8 inches)80%very high
October Weather12°C (54°F)129 mm (5.1 inches)82%high
November Weather4°C (39°F)57 mm (2.3 inches)88%moderate
December Weather0°C (33°F)53 mm (2.1 inches)84%low

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