Last updated: June 24, 2025
In December, the average temperature in Saint Charles, United States hovers around -4°C (26°F), with extremes ranging from a chilly -26°C (-14°F) to a surprisingly warm 18°C (65°F). During this time, you can expect about 43 mm (1.7 in) of precipitation spread across 7 days. The air will feel quite damp, with an average humidity of 82%.
In December in Saint Charles, the average temperature is -4°C (26°F), with a maximum that can reach 18°C (65°F) and a minimum that can be as low as -26°C (-14°F). Be prepared for a wide range of temperatures when traveling to Saint Charles during this time.
In Saint Charles in December, the total precipitation amount is 43 mm (1.7 in) spread over a period of 7 days.
In Saint Charles in December humidity is 82%. With an average temperature of -4°C (26°F), this humidity feels like an icy blanket enveloping you, making every step outside a battle against the chill and dampness—where the cold bites deeper, and the air feels heavy, reminding you that even in the winter, the moisture can be overwhelming for any traveler unprepared for such conditions.
In Saint Charles 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 Saint Charles, you can visit Hourly UV Index in Saint Charles.
UV Risk Categories
Weather in Saint Charles varies notably across the year, with each month offering distinct climate conditions. This page compares December’s weather to other months in Saint Charles, focusing on differences in temperature, rainfall, humidity, and UV levels.
| Temperature | Precipitation | Humidity | UV | |
|---|---|---|---|---|
| January Weather | -8°C (18°F) | 36 mm (1.4 inches) | 84% | moderate |
| February Weather | -7°C (19°F) | 48 mm (1.9 inches) | 85% | moderate |
| March Weather | 1°C (34°F) | 57 mm (2.2 inches) | 84% | moderate |
| April Weather | 7°C (44°F) | 86 mm (3.4 inches) | 83% | very high |
| May Weather | 15°C (59°F) | 152 mm (6.0 inches) | 75% | very high |
| June Weather | 21°C (71°F) | 151 mm (5.9 inches) | 79% | very high |
| July Weather | 23°C (74°F) | 103 mm (4.1 inches) | 75% | very high |
| August Weather | 21°C (70°F) | 126 mm (5.0 inches) | 69% | very high |
| September Weather | 18°C (64°F) | 117 mm (4.6 inches) | 74% | very high |
| October Weather | 9°C (49°F) | 118 mm (4.7 inches) | 79% | moderate |
| November Weather | 1°C (34°F) | 52 mm (2.0 inches) | 88% | moderate |
| December Weather | -4°C (26°F) | 43 mm (1.7 inches) | 82% | low |