Last updated: June 24, 2025
In September, the average temperature in Janesville, United States hovers around 19°C (66°F), offering a pleasant climate for visitors. However, be prepared for temperature fluctuations, as it can dip to a chilly 2°C (36°F) or soar to a warm 33°C (92°F). Residents and travelers alike should expect 116 mm (4.6 in) of precipitation spread over 10 days, contributing to a 75% humidity level that adds a touch of moisture to the air.
In September in Janesville, the average temperature is 19°C (66°F). The maximum can reach 33°C (92°F) and the minimum can be as low as 2°C (36°F). This diverse climate makes Janesville an ideal destination for travelers looking to experience a range of temperatures and activities.
In Janesville in September, the total precipitation amount is 116 mm (4.6 in) over a span of 10 days.
In Janesville in September humidity is 75%. With an average temperature of 19°C (66°F), this humidity feels like a warm, enveloping blanket, making it slightly uncomfortable for traveling as you navigate through the thick, muggy air.
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.
UV Risk Categories
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.
| Temperature | Precipitation | Humidity | UV | |
|---|---|---|---|---|
| January Weather | -7°C (20°F) | 40 mm (1.6 inches) | 82% | moderate |
| February Weather | -7°C (20°F) | 50 mm (2.0 inches) | 84% | moderate |
| March Weather | 2°C (36°F) | 72 mm (2.8 inches) | 80% | moderate |
| April Weather | 8°C (47°F) | 75 mm (2.9 inches) | 81% | very high |
| May Weather | 16°C (61°F) | 161 mm (6.3 inches) | 74% | very high |
| June Weather | 22°C (72°F) | 126 mm (5.0 inches) | 80% | extreme |
| July Weather | 24°C (75°F) | 97 mm (3.8 inches) | 80% | very high |
| August Weather | 22°C (71°F) | 113 mm (4.5 inches) | 77% | very high |
| September Weather | 19°C (66°F) | 116 mm (4.6 inches) | 75% | very high |
| October Weather | 10°C (51°F) | 132 mm (5.2 inches) | 80% | moderate |
| November Weather | 2°C (36°F) | 48 mm (1.9 inches) | 87% | moderate |
| December Weather | -2°C (29°F) | 35 mm (1.4 inches) | 83% | moderate |