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December Weather in Janesville, United States

Last updated: June 24, 2025

In Janesville, United States, the average temperature in December hovers around -1°C (30°F). Expect minimums dipping to -22°C (-7°F) and highs reaching up to 19°C (66°F). Precipitation averages 50 mm (2.0 in) spread over about 6 days, and the air is quite damp with an average humidity of 81%.

December Temperature in Janesville

In December in Janesville, the average temperature is -1°C (30°F), with maximums reaching up to 19°C (66°F) and minimums dropping as low as -22°C (-7°F). Travelers should be prepared for a wide range of temperatures, from chilly conditions to milder days.

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

The chart illustrates December 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, December typically has an average temperature of -1°C (30°F), with highs reaching up to 19°C (66°F) and lows dropping to around -22°C (-7°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.

December Precipitation in Janesville

In Janesville in December, the precipitation amount is 50 mm (2.0 in) over the course of 6 days.

December Precipitation Trends in Janesville

The chart displays monthly precipitation patterns in Janesville, with values for each month alongside December’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how December’s conditions compare to those of other months. In Janesville, December typically receives around 50 mm (2.0 inches) of precipitation spread over approximately 6 days.
JanFebMarAprMayJunJulAugSepOctNovDec58545910213411077941101114550
Data source: Precipitation data for December generated using information from the Copernicus Climate Change Service.
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December Humidity in Janesville

In Janesville in December, humidity is 81%. With an average temperature of -1°C (30°F), this humidity feels like an extra layer of chill settles in, making travel uncomfortable and the cold air cling to your skin, dampening the experience with every breath.

December Average Humidity in Janesville

This chart illustrates the average monthly humidity levels in Janesville, with December’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In December, average humidity in Janesville is approximately 81%, 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 December generated using information from the Copernicus Climate Change Service.

December UV Index in Janesville

In Janesville in December, the maximum UV index is 2, which corresponds to a low exposure category. With this level of UV radiation, the time to burn is approximately 45 minutes. To learn more about the hourly UV index in Janesville, you can visit Hourly UV Index in Janesville.

Maximum UV Index Levels in Janesville for December

The chart shows the monthly maximum UV Index (UVI) for Janesville in December, 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 December, the maximum UV index in Janesville typically reaches 2, which falls under the low exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec34689101098532
Data source: Janesville December 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 December 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 December’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 December’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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