Last updated: June 24, 2025
In December, the average temperature in Ontario, United States hovers around 1°C (34°F). Expect chilly lows of -14°C (7°F) and a pleasant peak of 17°C (63°F). During this time, 113 mm (4.4 in) of precipitation is typical, spread across about 20 days, contributing to an average humidity of a brisk 86%. Make sure to bundle up if you venture out!
In December in Ontario, the average temperature is 1°C (34°F). Maximum temperatures can reach 17°C (63°F), while minimums can drop as low as -14°C (7°F). Pack accordingly for your trip, as you may experience both chilly and mild weather.
In Ontario, in December, the precipitation amount is 113 mm (4.4 in) over the course of 20 days.
In Ontario in December, humidity is 86%. With an average temperature of 1°C (34°F), this humidity feels like a chilling embrace, making outdoor adventures brisk and invigorating but challenging for travel.
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.
UV Risk Categories
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.
Temperature | Precipitation | Humidity | UV | |
---|---|---|---|---|
January Weather | -2°C (29°F) | 94 mm (3.7 inches) | 90% | low |
February Weather | -1°C (30°F) | 94 mm (3.7 inches) | 90% | moderate |
March Weather | 2°C (35°F) | 85 mm (3.3 inches) | 87% | high |
April Weather | 6°C (44°F) | 124 mm (4.9 inches) | 88% | very high |
May Weather | 12°C (54°F) | 110 mm (4.3 inches) | 82% | very high |
June Weather | 18°C (64°F) | 80 mm (3.1 inches) | 79% | very high |
July Weather | 22°C (72°F) | 149 mm (5.9 inches) | 78% | very high |
August Weather | 22°C (72°F) | 103 mm (4.1 inches) | 76% | very high |
September Weather | 19°C (66°F) | 83 mm (3.3 inches) | 78% | high |
October Weather | 13°C (56°F) | 164 mm (6.5 inches) | 84% | moderate |
November Weather | 5°C (42°F) | 110 mm (4.3 inches) | 89% | moderate |
December Weather | 1°C (34°F) | 113 mm (4.4 inches) | 86% | low |