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December Weather in Cornwall, Canada

Last updated: June 18, 2025

In December, the average temperature in Cornwall, Canada hovers around -3°C (26°F). Expect a chilling minimum of -28°C (-19°F) and a surprisingly warmer maximum of 16°C (62°F). With 84 mm (3.3 in) of precipitation spread over 12 days, the air is quite moist, boasting an average humidity level of 89%.

December Temperature in Cornwall

In December in Cornwall, the average temperature is -3°C (26°F). The maximum can reach 16°C (62°F) and the minimum can be as low as -28°C (-19°F). Travelers should be prepared for a wide range of temperatures and pack accordingly for both chilly and milder conditions.

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

The chart illustrates December temperature patterns in Cornwall, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Cornwall, December typically has an average temperature of -3°C (26°F), with highs reaching up to 16°C (62°F) and lows dropping to around -28°C (-19°F).
JanFebMarAprMayJunJulAugSepOctNovDec192230435766716962503626
Data source: Temperature data for Cornwall 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 Cornwall

In Cornwall in December, the precipitation amount is 84 mm (3.3 in) over a span of 12 days.

December Precipitation Trends in Cornwall

The chart displays monthly precipitation patterns in Cornwall, 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 Cornwall, December typically receives around 84 mm (3.3 inches) of precipitation spread over approximately 12 days.
JanFebMarAprMayJunJulAugSepOctNovDec8583871171091001161007013910884
Data source: Precipitation data for December generated using information from the Copernicus Climate Change Service.
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December Humidity in Cornwall

In Cornwall in December, humidity is 89%. With an average temperature of -3°C (26°F), this humidity feels like a biting chill that seeps into your bones, making travel uncomfortable and requiring layered clothing to stay warm as you explore.

December Average Humidity in Cornwall

This chart illustrates the average monthly humidity levels in Cornwall, 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 Cornwall is approximately 89%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec93%92%86%85%80%74%76%75%78%86%89%89%
Data source: Humidity data for December generated using information from the Copernicus Climate Change Service.

December UV Index in Cornwall

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

Maximum UV Index Levels in Cornwall for December

The chart shows the monthly maximum UV Index (UVI) for Cornwall 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 Cornwall typically reaches 2, which falls under the low exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec245899987532
Data source: Cornwall 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 Cornwall Compares to Other Months

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

This table compares monthly weather conditions in Cornwall, showing how December’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-7°C (20°F)85 mm (3.3 inches)93%low
February Weather-6°C (22°F)83 mm (3.3 inches)92%moderate
March Weather-1°C (30°F)87 mm (3.4 inches)86%moderate
April Weather6°C (44°F)117 mm (4.6 inches)85%very high
May Weather14°C (57°F)109 mm (4.3 inches)80%very high
June Weather19°C (66°F)100 mm (3.9 inches)74%very high
July Weather22°C (72°F)116 mm (4.6 inches)76%very high
August Weather21°C (70°F)100 mm (3.9 inches)75%very high
September Weather16°C (62°F)70 mm (2.8 inches)78%high
October Weather10°C (51°F)139 mm (5.5 inches)86%moderate
November Weather2°C (36°F)108 mm (4.2 inches)88%moderate
December Weather-3°C (26°F)84 mm (3.3 inches)89%low

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