Last updated: June 24, 2025
The average temperature in St. Charles, United States during December is a chilly 6°C (43°F), with temperatures dipping as low as -9°C (16°F) and peaking at a cozy 20°C (68°F). Expect 86 mm (3.4 in) of precipitation spread across 9 days, contributing to an average humidity of a damp 84%. Be prepared for a mix of weather as you explore this captivating destination!
In December in St. Charles, the average temperature is 6°C (43°F), with maximums reaching 20°C (68°F) and minimums dipping as low as -9°C (16°F). It's advisable to prepare for varying weather conditions if you're planning to travel during this time.
In St. Charles in December, the precipitation amount is 86 mm (3.4 in), falling over the course of 9 days.
In St. Charles in December, humidity is 84%. With an average temperature of 6°C (43°F), this humidity feels like a damp chill that penetrates your clothing, making outdoor excursions uncomfortable and prompting travelers to seek refuge indoors or find warm, sheltered spots to enjoy their surroundings.
In St. Charles in December, the maximum UV index is 3, which corresponds to a moderate Exposure Category. The time to burn is approximately 30 minutes. For more details on the hourly UV index in St. Charles, you can check the information here.
UV Risk Categories
Weather in St. Charles varies notably across the year, with each month offering distinct climate conditions. This page compares December’s weather to other months in St. Charles, focusing on differences in temperature, rainfall, humidity, and UV levels.
| Temperature | Precipitation | Humidity | UV | |
|---|---|---|---|---|
| January Weather | 4°C (39°F) | 62 mm (2.4 inches) | 84% | moderate |
| February Weather | 6°C (42°F) | 93 mm (3.7 inches) | 83% | moderate |
| March Weather | 9°C (48°F) | 77 mm (3.0 inches) | 83% | high |
| April Weather | 14°C (58°F) | 99 mm (3.9 inches) | 81% | very high |
| May Weather | 19°C (67°F) | 118 mm (4.6 inches) | 78% | very high |
| June Weather | 24°C (76°F) | 106 mm (4.2 inches) | 79% | very high |
| July Weather | 27°C (81°F) | 122 mm (4.8 inches) | 74% | very high |
| August Weather | 26°C (79°F) | 151 mm (5.9 inches) | 72% | very high |
| September Weather | 23°C (73°F) | 91 mm (3.6 inches) | 75% | very high |
| October Weather | 17°C (64°F) | 108 mm (4.2 inches) | 81% | high |
| November Weather | 9°C (49°F) | 78 mm (3.1 inches) | 85% | moderate |
| December Weather | 6°C (43°F) | 86 mm (3.4 inches) | 84% | moderate |