Last updated: June 24, 2025
In December, the average temperature in Belfast, United States hovers around -1°C (30°F), with potential extremes ranging from a frigid -23°C (-10°F) to a mild 15°C (60°F). During this month, precipitation totals 87 mm (3.4 in), spread over approximately 15 days, contributing to an overall average humidity of 87%.
In December in Belfast, the average temperature is -1°C (30°F), with maximums reaching 15°C (60°F) and minimums plummeting to -23°C (-10°F). Travelers should prepare for a wide range of temperatures and dress accordingly for both chilly and mild conditions.
In Belfast in December, the precipitation amount is 87 mm (3.4 in) over the course of 15 days.
In Belfast in December, humidity is 87%. With an average temperature of -1°C (30°F), this humidity feels like a biting chill that penetrates through layers of clothing, making travel uncomfortable as the dampness clings to your skin, intensifying the cold and causing every gust of wind to feel even more frigid.
In Belfast 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 Belfast, you can visit Hourly UV Index in Belfast.
UV Risk Categories
Weather in Belfast varies notably across the year, with each month offering distinct climate conditions. This page compares December’s weather to other months in Belfast, focusing on differences in temperature, rainfall, humidity, and UV levels.
| Temperature | Precipitation | Humidity | UV | |
|---|---|---|---|---|
| January Weather | -4°C (24°F) | 78 mm (3.1 inches) | 91% | moderate |
| February Weather | -3°C (27°F) | 90 mm (3.5 inches) | 91% | moderate |
| March Weather | 1°C (34°F) | 80 mm (3.1 inches) | 88% | high |
| April Weather | 7°C (45°F) | 109 mm (4.3 inches) | 88% | very high |
| May Weather | 14°C (57°F) | 117 mm (4.6 inches) | 82% | very high |
| June Weather | 18°C (65°F) | 99 mm (3.9 inches) | 79% | very high |
| July Weather | 21°C (70°F) | 118 mm (4.7 inches) | 77% | very high |
| August Weather | 20°C (68°F) | 84 mm (3.3 inches) | 72% | very high |
| September Weather | 16°C (62°F) | 77 mm (3.0 inches) | 76% | very high |
| October Weather | 11°C (52°F) | 127 mm (5.0 inches) | 83% | high |
| November Weather | 3°C (37°F) | 85 mm (3.4 inches) | 88% | moderate |
| December Weather | -1°C (30°F) | 87 mm (3.4 inches) | 87% | low |