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September Weather in Janesville, United States

Last updated: June 24, 2025

In Janesville, United States, the average temperature in September hovers around 19°C (66°F). Temperatures can dip as low as 3°C (37°F) and reach a sultry 33°C (92°F). Expect approximately 110 mm (4.3 in) of precipitation spread over 10 days, with an average humidity of 79%, making it a month where the air feels both warm and damp.

September Temperature in Janesville

In September in Janesville, the average temperature is 19°C (66°F). Maximums can reach 33°C (92°F) and minimums can be as low as 3°C (37°F). This diverse temperature range makes Janesville an ideal destination for travelers looking for a mix of warm and cool weather during their visit.

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

The chart illustrates September temperature patterns in Janesville, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Janesville, September typically has an average temperature of 19°C (66°F), with highs reaching up to 33°C (92°F) and lows dropping to around 3°C (37°F).
JanFebMarAprMayJunJulAugSepOctNovDec222337466071757266523730
Data source: Temperature data for Janesville 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 Janesville

In Janesville in September, the precipitation amount is 110 mm (4.3 in) over a period of 10 days.

September Precipitation Trends in Janesville

The chart displays monthly precipitation patterns in Janesville, 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 Janesville, September typically receives around 110 mm (4.3 inches) of precipitation spread over approximately 10 days.
JanFebMarAprMayJunJulAugSepOctNovDec58545910213411077941101114550
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Janesville

In Janesville in September humidity is 79%. With an average temperature of 19°C (66°F), this humidity feels like a warm embrace, making it feel much warmer than the actual temperature and creating a heavy, sticky atmosphere that can be a bit uncomfortable for traveling.

September Average Humidity in Janesville

This chart illustrates the average monthly humidity levels in Janesville, 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 Janesville is approximately 79%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec85%85%85%85%78%80%78%76%79%83%88%82%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Janesville

In Janesville 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 Janesville.

Maximum UV Index Levels in Janesville for September

The chart shows the monthly maximum UV Index (UVI) for Janesville 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 Janesville typically reaches 8, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec34689101098532
Data source: Janesville 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 Janesville Compares to Other Months

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

This table compares monthly weather conditions in Janesville, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-6°C (22°F)58 mm (2.3 inches)85%moderate
February Weather-5°C (24°F)54 mm (2.1 inches)85%moderate
March Weather3°C (37°F)59 mm (2.3 inches)85%high
April Weather8°C (47°F)102 mm (4.0 inches)85%very high
May Weather15°C (60°F)133 mm (5.3 inches)78%very high
June Weather22°C (71°F)110 mm (4.3 inches)80%very high
July Weather24°C (75°F)77 mm (3.0 inches)78%very high
August Weather22°C (72°F)94 mm (3.7 inches)76%very high
September Weather19°C (66°F)110 mm (4.3 inches)79%very high
October Weather11°C (52°F)111 mm (4.4 inches)83%moderate
November Weather3°C (37°F)45 mm (1.8 inches)88%moderate
December Weather-1°C (30°F)50 mm (2.0 inches)81%low

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