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December Weather in Alton, United States

Last updated: June 24, 2025

In December, the average temperature in Alton, United States hovers around -2°C (29°F), with potential extremes ranging from a chilly -23°C (-8°F) to a milder 15°C (60°F). Expect about 119 mm (4.7 in) of precipitation spread over 10 days, coupled with an average humidity of 81%. Be prepared for a wet and cold experience!

December Temperature in Alton

In December in Alton, average temperature is -2°C (29°F). Maximum can reach 15°C (60°F) and minimum can be as low as -23°C (-8°F). Be prepared for a wide range of temperatures, making it essential to pack layers for your trip.

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

The chart illustrates December temperature patterns in Alton, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Alton, December typically has an average temperature of -2°C (29°F), with highs reaching up to 15°C (60°F) and lows dropping to around -23°C (-8°F).
JanFebMarAprMayJunJulAugSepOctNovDec242633445566727164523829
Data source: Temperature data for Alton 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 Alton

In Alton in December, the total precipitation amount is 119 mm (4.7 in) over the span of 10 days.

December Precipitation Trends in Alton

The chart displays monthly precipitation patterns in Alton, 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 Alton, December typically receives around 119 mm (4.7 inches) of precipitation spread over approximately 10 days.
JanFebMarAprMayJunJulAugSepOctNovDec75847712874871347466119110119
Data source: Precipitation data for December generated using information from the Copernicus Climate Change Service.
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December Humidity in Alton

In Alton in December humidity is 81%. With an average temperature of -2°C (29°F), this humidity feels like an uncomfortable chill that seeps into your bones, making outdoor activities less enjoyable and requiring extra layers to stay warm while traveling.

December Average Humidity in Alton

This chart illustrates the average monthly humidity levels in Alton, 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 Alton is approximately 81%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec86%84%82%80%72%72%67%66%71%79%84%81%
Data source: Humidity data for December generated using information from the Copernicus Climate Change Service.

December UV Index in Alton

In Alton 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 Alton, you can visit Hourly UV Index in Alton.

Maximum UV Index Levels in Alton for December

The chart shows the monthly maximum UV Index (UVI) for Alton 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 Alton typically reaches 2, which falls under the low exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec3458910997532
Data source: Alton 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 Alton Compares to Other Months

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

This table compares monthly weather conditions in Alton, showing how December’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-5°C (24°F)75 mm (2.9 inches)86%moderate
February Weather-3°C (27°F)84 mm (3.3 inches)84%moderate
March Weather0°C (33°F)77 mm (3.0 inches)82%moderate
April Weather7°C (44°F)128 mm (5.0 inches)80%very high
May Weather13°C (56°F)74 mm (2.9 inches)72%very high
June Weather19°C (66°F)87 mm (3.4 inches)72%very high
July Weather22°C (72°F)134 mm (5.3 inches)67%very high
August Weather21°C (71°F)74 mm (2.9 inches)66%very high
September Weather18°C (64°F)66 mm (2.6 inches)71%high
October Weather11°C (52°F)119 mm (4.7 inches)78%moderate
November Weather3°C (39°F)110 mm (4.3 inches)84%moderate
December Weather-2°C (29°F)119 mm (4.7 inches)81%low

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