Last updated: June 24, 2025
In Johnstown, United States, the average temperature in December hovers around -2°C (29°F), with extremes ranging from a chilling -24°C (-11°F) to a mild 16°C (62°F). Expect 108 mm (4.2 in) of precipitation spread over 12 days, contributing to an average humidity of 84%. Prepare for a month that combines frosty air with occasional wet spells!
In December in Johnstown, the average temperature is -2°C (29°F), with maximums that can reach 16°C (62°F) and minimums that can plummet to -24°C (-11°F). Travelers should be prepared for a wide range of temperatures, ensuring they pack both warm clothing for the chilly lows and lighter layers for the occasional warmer days.
In Johnstown in December, the total precipitation amount is 108 mm (4.2 in) spread over 12 days.
In Johnstown in December, humidity is 84%. With an average temperature of -2°C (29°F), this humidity feels like an icy blanket that clings to your skin, making it difficult to stay warm and comfortable while traveling.
In Johnstown 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 Johnstown, you can visit Hourly UV Index in Johnstown.
UV Risk Categories
Weather in Johnstown varies notably across the year, with each month offering distinct climate conditions. This page compares December’s weather to other months in Johnstown, focusing on differences in temperature, rainfall, humidity, and UV levels.
| Temperature | Precipitation | Humidity | UV | |
|---|---|---|---|---|
| January Weather | -5°C (24°F) | 85 mm (3.3 inches) | 89% | moderate |
| February Weather | -3°C (26°F) | 101 mm (4.0 inches) | 88% | moderate |
| March Weather | 0°C (33°F) | 84 mm (3.3 inches) | 86% | high |
| April Weather | 7°C (45°F) | 129 mm (5.1 inches) | 84% | very high |
| May Weather | 14°C (58°F) | 108 mm (4.2 inches) | 76% | very high |
| June Weather | 19°C (66°F) | 98 mm (3.9 inches) | 72% | very high |
| July Weather | 22°C (72°F) | 121 mm (4.7 inches) | 66% | very high |
| August Weather | 21°C (70°F) | 100 mm (3.9 inches) | 64% | very high |
| September Weather | 17°C (63°F) | 90 mm (3.5 inches) | 72% | high |
| October Weather | 11°C (52°F) | 158 mm (6.2 inches) | 81% | high |
| November Weather | 3°C (38°F) | 105 mm (4.1 inches) | 87% | moderate |
| December Weather | -2°C (29°F) | 108 mm (4.2 inches) | 84% | low |