September Weather in Janesville, United States

Last updated: June 24, 2025

In Janesville, United States, the average temperature in September hovers around 17°C (63°F), making it a pleasant time to visit. However, be prepared for a range, as temperatures can dip to a brisk -1°C (30°F) or soar to a sweltering 36°C (97°F). During this month, expect 19 mm (0.7 in) of precipitation spread over 3 days, with an average humidity level of 46%, perfect for enjoying the outdoors while staying comfortable.

September Temperature in Janesville

In September in Janesville, the average temperature is 17°C (63°F), with maximums reaching 36°C (97°F) and minimums dropping as low as -1°C (30°F). It's a time of year when travelers should be prepared for a wide range of weather conditions, making it essential to pack accordingly.

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 17°C (63°F), with highs reaching up to 36°C (97°F) and lows dropping to around -1°C (30°F).

Data source: Temperature data for Janesville generated using information from the Copernicus Climate Change Service.

September Precipitation in Janesville

In Janesville in September, the precipitation amount is 19 mm (0.7 in) over a period of 3 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 19 mm (0.7 inches) of precipitation spread over approximately 3 days.

Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.

Choose your preferred precipitation unit

Millimeters (mm) Inches (in)

September Humidity in Janesville

In Janesville in September, humidity is 46%. With an average temperature of 17°C (63°F), this humidity feels like a mild embrace—comfortable for exploring the sights, though you might notice a slight heaviness in the air that encourages a leisurely pace as you take in the vibrant surroundings.

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 46%, offering insight into how humid the weather typically is during this month.

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 9, which corresponds to a very high Exposure Category. The time to burn is just 15 minutes, so it's essential to take precautions. For detailed information, you can check 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 9, which falls under the very high exposure category.

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.
	Temperature	Precipitation	Humidity	UV
January Weather	0°C (32°F)	102 mm (4.0 inches)	86%	moderate
February Weather	0°C (32°F)	110 mm (4.3 inches)	87%	moderate
March Weather	2°C (37°F)	85 mm (3.4 inches)	86%	very high
April Weather	8°C (46°F)	43 mm (1.7 inches)	83%	very high
May Weather	12°C (55°F)	44 mm (1.7 inches)	72%	extreme
June Weather	19°C (66°F)	10 mm (0.4 inches)	67%	extreme
July Weather	23°C (74°F)	7 mm (0.3 inches)	56%	extreme
August Weather	22°C (72°F)	8 mm (0.3 inches)	42%	extreme
September Weather	17°C (63°F)	19 mm (0.7 inches)	46%	very high
October Weather	10°C (50°F)	34 mm (1.3 inches)	67%	high
November Weather	4°C (40°F)	47 mm (1.8 inches)	86%	moderate
December Weather	-1°C (31°F)	75 mm (3.0 inches)	86%	moderate