Last updated: June 18, 2025
In Thunder Bay, Canada, the average temperature in December hovers around -9°C (16°F). However, be prepared for extremes, as temperatures can plunge to a chilling -32°C (-26°F) or rise to a mild 8°C (47°F). During this month, you can expect about 55 mm (2.2 in) of precipitation spread over 7 days, with an unusually high average humidity of 94%.
In December in Thunder Bay, the average temperature is -9°C (16°F). The maximum can reach 8°C (47°F), while the minimum can plummet to as low as -32°C (-26°F). Travelers should be prepared for extremely cold conditions and dress warmly to enjoy outdoor activities.
In Thunder Bay in December, the precipitation amount is 55 mm (2.2 in) over the course of 7 days.
In Thunder Bay in December humidity is 94%. With an average temperature of -9°C (16°F), this humidity feels like an icy blanket enveloping you, making every breath a struggle and the air seemingly heavy. Traveling under these conditions can be challenging, as the cold dampness seeps into your clothes, chilling you to the bone and complicating outdoor activities.
In Thunder Bay in December, the maximum UV index is 1, which corresponds to a low Exposure Category. This means you have a time to burn of 45 minutes. For more details, you can check the Hourly UV Index in Thunder Bay.
UV Risk Categories
Weather in Thunder Bay varies notably across the year, with each month offering distinct climate conditions. This page compares December’s weather to other months in Thunder Bay, focusing on differences in temperature, rainfall, humidity, and UV levels.
| Temperature | Precipitation | Humidity | UV | |
|---|---|---|---|---|
| January Weather | -13°C (9°F) | 30 mm (1.2 inches) | 95% | low |
| February Weather | -13°C (9°F) | 35 mm (1.4 inches) | 94% | moderate |
| March Weather | -5°C (23°F) | 31 mm (1.2 inches) | 92% | moderate |
| April Weather | 1°C (33°F) | 58 mm (2.3 inches) | 90% | high |
| May Weather | 8°C (47°F) | 52 mm (2.0 inches) | 78% | very high |
| June Weather | 14°C (58°F) | 58 mm (2.3 inches) | 71% | very high |
| July Weather | 19°C (66°F) | 82 mm (3.2 inches) | 70% | very high |
| August Weather | 17°C (63°F) | 77 mm (3.0 inches) | 72% | very high |
| September Weather | 13°C (55°F) | 98 mm (3.9 inches) | 76% | high |
| October Weather | 6°C (43°F) | 87 mm (3.4 inches) | 82% | moderate |
| November Weather | -3°C (27°F) | 51 mm (2.0 inches) | 87% | low |
| December Weather | -9°C (16°F) | 55 mm (2.2 inches) | 94% | low |