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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 6°C (42°F). However, be prepared for a variety of conditions, as temperatures can drop to a chilling -12°C (11°F) or soar to a pleasant 25°C (77°F). Expect an average of 81 mm (3.2 in) of precipitation spread over 8 days, accompanied by a high average humidity of 86%. Embrace the diversity of the season!

December Temperature in Alton

In December in Alton, the average temperature is 6°C (42°F). Maximums can reach 25°C (77°F) and minimums can be as low as -12°C (11°F). It's advisable to pack layers to prepare for a wide range of temperatures during your travels.

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 6°C (42°F), with highs reaching up to 25°C (77°F) and lows dropping to around -12°C (11°F).
JanFebMarAprMayJunJulAugSepOctNovDec363950566775807773604642
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 precipitation amount is 81 mm (3.2 in) over the course of 8 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 81 mm (3.2 inches) of precipitation spread over approximately 8 days.
JanFebMarAprMayJunJulAugSepOctNovDec851111481641818580107621217781
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 86%. With an average temperature of 6°C (42°F), this humidity feels like a chilly, damp embrace that can make outdoor activities feel uncomfortable and chilly, prompting travelers to seek shelter or warm clothing to stay cozy while exploring.

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 86%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec83%81%80%80%83%83%76%69%68%72%83%87%
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 3, which corresponds to a moderate Exposure Category. The time to burn is approximately 30 minutes. For more details on the hourly UV index in Alton, you can check the information here.

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 3, which falls under the moderate exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec36710111111109753
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 Weather2°C (36°F)85 mm (3.3 inches)83%moderate
February Weather4°C (40°F)111 mm (4.4 inches)81%high
March Weather10°C (50°F)148 mm (5.8 inches)80%high
April Weather13°C (56°F)164 mm (6.5 inches)80%very high
May Weather19°C (67°F)181 mm (7.1 inches)83%extreme
June Weather24°C (76°F)85 mm (3.3 inches)83%extreme
July Weather26°C (80°F)80 mm (3.2 inches)76%extreme
August Weather25°C (77°F)106 mm (4.2 inches)69%very high
September Weather23°C (73°F)62 mm (2.4 inches)68%very high
October Weather16°C (60°F)121 mm (4.8 inches)72%high
November Weather8°C (47°F)77 mm (3.0 inches)83%moderate
December Weather6°C (42°F)81 mm (3.2 inches)86%moderate

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