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September Weather in Rock Falls, United States

Last updated: June 24, 2025

In Rock Falls, United States, the average temperature in September hovers around 20°C (68°F). Expect a minimum of 3°C (38°F) and a maximum that can soar up to 35°C (95°F). Be prepared for about 115 mm (4.5 in) of precipitation scattered over 10 days, and note that the average humidity tends to be 80%.

September Temperature in Rock Falls

In September in Rock Falls, the average temperature is 20°C (68°F). Maximums can reach up to 35°C (95°F), while minimums can drop as low as 3°C (38°F). Be sure to pack a variety of clothing to accommodate the temperature fluctuations during your travels.

September Weather in Rock Falls: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in Rock Falls, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Rock Falls, September typically has an average temperature of 20°C (68°F), with highs reaching up to 35°C (95°F) and lows dropping to around 3°C (38°F).
JanFebMarAprMayJunJulAugSepOctNovDec232640496273767368543932
Data source: Temperature data for Rock Falls 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 Rock Falls

In Rock Falls in September, the precipitation amount is 115 mm (4.5 in) over a span of 10 days.

September Precipitation Trends in Rock Falls

The chart displays monthly precipitation patterns in Rock Falls, 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 Rock Falls, September typically receives around 115 mm (4.5 inches) of precipitation spread over approximately 10 days.
JanFebMarAprMayJunJulAugSepOctNovDec59598611015714198731151155250
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Rock Falls

In Rock Falls 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 Rock Falls

This chart illustrates the average monthly humidity levels in Rock Falls, 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 Rock Falls 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 Rock Falls

In Rock Falls 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 Rock Falls.

Maximum UV Index Levels in Rock Falls for September

The chart shows the monthly maximum UV Index (UVI) for Rock Falls 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 Rock Falls typically reaches 8, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec35689101098642
Data source: Rock Falls 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 Rock Falls Compares to Other Months

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

This table compares monthly weather conditions in Rock Falls, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-5°C (24°F)59 mm (2.3 inches)82%moderate
February Weather-3°C (26°F)59 mm (2.3 inches)83%moderate
March Weather4°C (40°F)86 mm (3.4 inches)84%high
April Weather9°C (49°F)110 mm (4.3 inches)85%very high
May Weather17°C (62°F)157 mm (6.2 inches)79%very high
June Weather23°C (73°F)141 mm (5.6 inches)82%very high
July Weather24°C (76°F)98 mm (3.8 inches)80%very high
August Weather23°C (73°F)73 mm (2.9 inches)81%very high
September Weather20°C (68°F)115 mm (4.5 inches)80%very high
October Weather12°C (54°F)115 mm (4.5 inches)82%high
November Weather4°C (39°F)51 mm (2.0 inches)88%moderate
December Weather0°C (32°F)50 mm (2.0 inches)84%low

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