Last updated: June 24, 2025
In December, the average temperature in Merrimack, United States hovers around 0°C (32°F), making for a chilly atmosphere. You might experience temperatures dipping as low as -21°C (-5°F) and peaking at a mild 17°C (62°F). Expect some precipitation, totaling 120 mm (4.7 in) over approximately 9 days, and keep in mind the average humidity is a noteworthy 81%.
In December in Merrimack, the average temperature is 0°C (32°F). The maximum can reach 17°C (62°F), while the minimum can drop as low as -21°C (-5°F). Travelers should be prepared for a wide range of temperatures, ensuring both warm and warm clothing options are packed.
In Merrimack in December, the precipitation amount is 120 mm (4.7 in) over the course of 9 days.
In Merrimack in December, humidity is 81%. With an average temperature of 0°C (32°F), this humidity feels like a damp chill that seeps into your bones, making outdoor activities less enjoyable and requiring extra layers to stay warm and dry while traveling.
In Merrimack 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 Merrimack, you can visit Hourly UV Index in Merrimack.
UV Risk Categories
Weather in Merrimack varies notably across the year, with each month offering distinct climate conditions. This page compares December’s weather to other months in Merrimack, focusing on differences in temperature, rainfall, humidity, and UV levels.
| Temperature | Precipitation | Humidity | UV | |
|---|---|---|---|---|
| January Weather | -2°C (29°F) | 71 mm (2.8 inches) | 86% | moderate |
| February Weather | -1°C (31°F) | 84 mm (3.3 inches) | 84% | moderate |
| March Weather | 2°C (37°F) | 82 mm (3.2 inches) | 82% | moderate |
| April Weather | 9°C (48°F) | 126 mm (5.0 inches) | 80% | very high |
| May Weather | 15°C (59°F) | 81 mm (3.2 inches) | 72% | very high |
| June Weather | 20°C (69°F) | 85 mm (3.3 inches) | 72% | very high |
| July Weather | 23°C (74°F) | 136 mm (5.4 inches) | 67% | very high |
| August Weather | 23°C (73°F) | 85 mm (3.4 inches) | 66% | very high |
| September Weather | 19°C (66°F) | 77 mm (3.0 inches) | 71% | high |
| October Weather | 12°C (55°F) | 128 mm (5.0 inches) | 78% | high |
| November Weather | 5°C (41°F) | 98 mm (3.9 inches) | 84% | moderate |
| December Weather | 0°C (32°F) | 120 mm (4.7 inches) | 81% | low |