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December Weather in Keystone, United States

Last updated: June 24, 2025

In December, the average temperature in Keystone, United States hovers around -1°C (30°F). Expect a chilly range, with minimums plummeting to -22°C (-8°F) and occasional peaks reaching 23°C (73°F). Don’t forget your umbrella, as the area experiences 40 mm (1.6 in) of precipitation over 5 days. With an average humidity of 84%, brace yourself for a wet and cold experience!

December Temperature in Keystone

In December in Keystone, the average temperature is -1°C (30°F), with maximums reaching 23°C (73°F) and minimums dropping as low as -22°C (-8°F). Travelers should be prepared for a wide range of temperatures, from chilly to pleasantly warm, making it essential to pack accordingly.

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

The chart illustrates December temperature patterns in Keystone, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Keystone, December typically has an average temperature of -1°C (30°F), with highs reaching up to 23°C (73°F) and lows dropping to around -22°C (-8°F).
JanFebMarAprMayJunJulAugSepOctNovDec212338486273757267523730
Data source: Temperature data for Keystone 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 Keystone

In Keystone in December, the precipitation amount is 40 mm (1.6 in) over the course of 5 days.

December Precipitation Trends in Keystone

The chart displays monthly precipitation patterns in Keystone, 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 Keystone, December typically receives around 40 mm (1.6 inches) of precipitation spread over approximately 5 days.
JanFebMarAprMayJunJulAugSepOctNovDec4552738516214391641211434540
Data source: Precipitation data for December generated using information from the Copernicus Climate Change Service.
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December Humidity in Keystone

In Keystone in December, humidity is 84%. With an average temperature of -1°C (30°F), this humidity feels like a sharp chill that seeps into your bones, making travel uncomfortable as the wetness in the air intensifies the cold, leaving you yearning for warmth and shelter.

December Average Humidity in Keystone

This chart illustrates the average monthly humidity levels in Keystone, 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 Keystone is approximately 84%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec81%81%81%82%78%81%79%77%78%79%87%84%
Data source: Humidity data for December generated using information from the Copernicus Climate Change Service.

December UV Index in Keystone

In Keystone 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 Keystone, you can check the information here.

Maximum UV Index Levels in Keystone for December

The chart shows the monthly maximum UV Index (UVI) for Keystone 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 Keystone typically reaches 3, which falls under the moderate exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec35689111098633
Data source: Keystone 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 Keystone Compares to Other Months

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

This table compares monthly weather conditions in Keystone, showing how December’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-6°C (21°F)45 mm (1.8 inches)81%moderate
February Weather-5°C (23°F)52 mm (2.1 inches)81%moderate
March Weather3°C (38°F)73 mm (2.9 inches)81%high
April Weather9°C (48°F)85 mm (3.3 inches)82%very high
May Weather16°C (62°F)162 mm (6.4 inches)78%very high
June Weather23°C (73°F)143 mm (5.6 inches)81%extreme
July Weather24°C (76°F)91 mm (3.6 inches)79%very high
August Weather22°C (72°F)64 mm (2.5 inches)77%very high
September Weather20°C (67°F)121 mm (4.8 inches)78%very high
October Weather11°C (52°F)143 mm (5.6 inches)78%high
November Weather3°C (38°F)45 mm (1.8 inches)87%moderate
December Weather-1°C (30°F)40 mm (1.6 inches)84%moderate

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