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September Weather in Winnetka, United States

Last updated: June 24, 2025

In September, the average temperature in Winnetka, United States is a comfortable 20°C (68°F). However, temperatures can vary, with a minimum of 6°C (44°F) and a maximum of 31°C (88°F). During this month, expect about 79 mm (3.1 in) of precipitation spread over roughly 10 days, contributing to an average humidity of 80%.

September Temperature in Winnetka

In September in Winnetka, the average temperature is 20°C (68°F). The maximum can reach 31°C (88°F) and the minimum can be as low as 6°C (44°F). This pleasant climate makes Winnetka an ideal destination for travelers seeking a comfortable getaway.

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

The chart illustrates September temperature patterns in Winnetka, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Winnetka, September typically has an average temperature of 20°C (68°F), with highs reaching up to 31°C (88°F) and lows dropping to around 6°C (44°F).
JanFebMarAprMayJunJulAugSepOctNovDec272838465768747368554034
Data source: Temperature data for Winnetka 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 Winnetka

In Winnetka in September, the precipitation amount is 79 mm (3.1 in) over a span of 10 days.

September Precipitation Trends in Winnetka

The chart displays monthly precipitation patterns in Winnetka, 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 Winnetka, September typically receives around 79 mm (3.1 inches) of precipitation spread over approximately 10 days.
JanFebMarAprMayJunJulAugSepOctNovDec6667821161591239480791346258
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Winnetka

In Winnetka 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 Winnetka

This chart illustrates the average monthly humidity levels in Winnetka, 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 Winnetka 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 Winnetka

In Winnetka 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 Winnetka.

Maximum UV Index Levels in Winnetka for September

The chart shows the monthly maximum UV Index (UVI) for Winnetka 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 Winnetka typically reaches 8, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec34689101098632
Data source: Winnetka 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 Winnetka Compares to Other Months

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

This table compares monthly weather conditions in Winnetka, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-3°C (27°F)66 mm (2.6 inches)82%moderate
February Weather-2°C (29°F)66 mm (2.6 inches)83%moderate
March Weather3°C (38°F)82 mm (3.2 inches)84%high
April Weather8°C (46°F)116 mm (4.6 inches)85%very high
May Weather14°C (57°F)159 mm (6.2 inches)79%very high
June Weather20°C (68°F)123 mm (4.8 inches)82%very high
July Weather23°C (74°F)94 mm (3.7 inches)80%very high
August Weather23°C (73°F)80 mm (3.2 inches)81%very high
September Weather20°C (68°F)79 mm (3.1 inches)80%very high
October Weather13°C (55°F)134 mm (5.3 inches)82%high
November Weather4°C (40°F)62 mm (2.4 inches)88%moderate
December Weather1°C (34°F)58 mm (2.3 inches)84%low

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