Last updated: June 24, 2025
In December, the average temperature in Southwest Harbor, United States hovers around 1°C (35°F), with fluctuations ranging from a chilly -16°C (4°F) to a mild 14°C (57°F). Expect about 154 mm (6.1 in) of precipitation over 13 days, accompanied by relatively high humidity at 84%. Be prepared for a mix of cold and wet weather during this time!
In December, in Southwest Harbor, the average temperature is a chilly 1°C (35°F). Maximum temperatures can reach a milder 14°C (57°F), while the minimum can drop as low as -16°C (4°F). Travelers should prepare for cold weather and pack accordingly for their trip.
In Southwest Harbor in December, the precipitation amount is 154 mm (6.1 in) over the course of 13 days.
In Southwest Harbor in December humidity is 84%. With an average temperature of 1°C (35°F), this humidity feels like a cold, damp chill that seeps into your bones, making it feel much colder than the thermometer suggests, which can be quite uncomfortable for traveling.
In Southwest Harbor 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 Southwest Harbor, you can visit Hourly UV Index in Southwest Harbor.
UV Risk Categories
Weather in Southwest Harbor varies notably across the year, with each month offering distinct climate conditions. This page compares December’s weather to other months in Southwest Harbor, focusing on differences in temperature, rainfall, humidity, and UV levels.
| Temperature | Precipitation | Humidity | UV | |
|---|---|---|---|---|
| January Weather | -1°C (30°F) | 113 mm (4.4 inches) | 88% | low |
| February Weather | -1°C (31°F) | 107 mm (4.2 inches) | 88% | moderate |
| March Weather | 1°C (34°F) | 83 mm (3.3 inches) | 85% | moderate |
| April Weather | 5°C (41°F) | 143 mm (5.6 inches) | 81% | high |
| May Weather | 8°C (48°F) | 105 mm (4.1 inches) | 76% | very high |
| June Weather | 12°C (54°F) | 95 mm (3.7 inches) | 74% | very high |
| July Weather | 15°C (59°F) | 82 mm (3.2 inches) | 74% | very high |
| August Weather | 16°C (62°F) | 87 mm (3.4 inches) | 74% | very high |
| September Weather | 15°C (59°F) | 105 mm (4.2 inches) | 77% | high |
| October Weather | 12°C (54°F) | 119 mm (4.7 inches) | 82% | moderate |
| November Weather | 6°C (44°F) | 139 mm (5.5 inches) | 85% | moderate |
| December Weather | 1°C (35°F) | 154 mm (6.1 inches) | 84% | low |