Last updated: June 24, 2025
In Groton, United States, the average temperature in December hovers around 4°C (40°F). During this time, you can expect a minimum chill of -11°C (12°F) and a pleasant maximum of 16°C (61°F). Be prepared for some moisture, as precipitation totals reach 141 mm (5.6 in) over approximately 11 days, while the air remains relatively damp with an average humidity of 80%.
In December in Groton, the average temperature is 4°C (40°F). Maximum temperatures can reach 16°C (61°F), while minimums can plummet to -11°C (12°F). Travelers should be prepared for a wide range of temperatures and pack accordingly.
In Groton in December, the total precipitation amount is 141 mm (5.6 in) spread over 11 days.
In Groton in December, humidity is 80%. With an average temperature of 4°C (40°F), this humidity feels like a damp chill that seeps into your bones, making travel uncomfortable and requiring careful planning for warmth and moisture management.
In Groton 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 Groton, you can visit Hourly UV Index in Groton.
UV Risk Categories
Weather in Groton varies notably across the year, with each month offering distinct climate conditions. This page compares December’s weather to other months in Groton, focusing on differences in temperature, rainfall, humidity, and UV levels.
| Temperature | Precipitation | Humidity | UV | |
|---|---|---|---|---|
| January Weather | 2°C (35°F) | 83 mm (3.3 inches) | 84% | moderate |
| February Weather | 2°C (36°F) | 109 mm (4.3 inches) | 84% | moderate |
| March Weather | 4°C (39°F) | 108 mm (4.3 inches) | 82% | high |
| April Weather | 8°C (47°F) | 136 mm (5.3 inches) | 79% | very high |
| May Weather | 13°C (55°F) | 119 mm (4.7 inches) | 75% | very high |
| June Weather | 18°C (64°F) | 84 mm (3.3 inches) | 78% | very high |
| July Weather | 22°C (72°F) | 115 mm (4.5 inches) | 76% | very high |
| August Weather | 22°C (73°F) | 101 mm (4.0 inches) | 76% | very high |
| September Weather | 20°C (68°F) | 101 mm (4.0 inches) | 75% | very high |
| October Weather | 16°C (60°F) | 157 mm (6.2 inches) | 75% | high |
| November Weather | 9°C (49°F) | 113 mm (4.4 inches) | 80% | moderate |
| December Weather | 4°C (40°F) | 141 mm (5.6 inches) | 80% | low |