December Weather in Ontario, United States

Last updated: June 24, 2025

In December, the average temperature in Ontario, United States hovers around -3°C (27°F), though it can plunge as low as -24°C (-11°F) or soar up to 17°C (64°F). With an average humidity of 82%, prepare for a chilly atmosphere. Expect about 46 mm (1.8 in) of precipitation spread over 6 days, adding to the wintery charm of the region.

December Temperature in Ontario

In December in Ontario, the average temperature is -3°C (27°F). Maximums can reach 17°C (64°F), while minimums can drop as low as -24°C (-11°F). Travelers should be prepared for a wide temperature range and dress accordingly for a comfortable experience.

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

The chart illustrates December temperature patterns in Ontario, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Ontario, December typically has an average temperature of -3°C (27°F), with highs reaching up to 17°C (64°F) and lows dropping to around -24°C (-11°F).

Data source: Temperature data for Ontario generated using information from the Copernicus Climate Change Service.

December Precipitation in Ontario

In Ontario in December, the precipitation amount is 46 mm (1.8 in) over a span of 6 days.

December Precipitation Trends in Ontario

The chart displays monthly precipitation patterns in Ontario, 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 Ontario, December typically receives around 46 mm (1.8 inches) of precipitation spread over approximately 6 days.

Data source: Precipitation data for December generated using information from the Copernicus Climate Change Service.

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Millimeters (mm) Inches (in)

December Humidity in Ontario

In Ontario in December, humidity is 82%. With an average temperature of -3°C (27°F), this humidity feels like a biting chill that seeps into your bones, making traveling uncomfortable and necessitating extra layers to stay warm while navigating through the damp air.

December Average Humidity in Ontario

This chart illustrates the average monthly humidity levels in Ontario, 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 Ontario is approximately 82%, offering insight into how humid the weather typically is during this month.

Data source: Humidity data for December generated using information from the Copernicus Climate Change Service.

December UV Index in Ontario

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

Maximum UV Index Levels in Ontario for December

The chart shows the monthly maximum UV Index (UVI) for Ontario 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 Ontario typically reaches 2, which falls under the low exposure category.

Data source: Ontario 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 Ontario Compares to Other Months

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

This table compares monthly weather conditions in Ontario, showing how December’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
	Temperature	Precipitation	Humidity	UV
January Weather	-7°C (20°F)	40 mm (1.6 inches)	84%	low
February Weather	-6°C (21°F)	54 mm (2.1 inches)	85%	moderate
March Weather	2°C (35°F)	59 mm (2.3 inches)	84%	moderate
April Weather	7°C (45°F)	91 mm (3.6 inches)	83%	very high
May Weather	15°C (59°F)	141 mm (5.5 inches)	75%	very high
June Weather	21°C (70°F)	121 mm (4.8 inches)	79%	very high
July Weather	23°C (74°F)	110 mm (4.3 inches)	75%	very high
August Weather	21°C (70°F)	117 mm (4.6 inches)	69%	very high
September Weather	18°C (64°F)	112 mm (4.4 inches)	74%	very high
October Weather	10°C (50°F)	115 mm (4.5 inches)	79%	moderate
November Weather	2°C (35°F)	52 mm (2.0 inches)	88%	moderate
December Weather	-3°C (27°F)	46 mm (1.8 inches)	82%	low