Last updated: June 24, 2025
In Alton, United States, the average temperature in December hovers around -3°C (27°F). Be prepared for temperature extremes, as the minimum can dip as low as -24°C (-10°F), while the maximum can reach a pleasant 19°C (66°F). During this period, expect 39 mm (1.5 in) of precipitation spread over 4 days, and enjoy the crisp air with an average humidity of around 83%.
In December in Alton, the average temperature is -3°C (27°F), with a maximum that can reach 19°C (66°F) and a minimum that can drop as low as -24°C (-10°F). Be sure to pack for a wide range of temperatures when traveling to Alton this month.
In Alton in December, the precipitation amount is 39 mm (1.5 in) spread over a period of 4 days.
In Alton in December humidity is 83%. With an average temperature of -3°C (27°F), this humidity feels like a biting chill that wraps around you, making every breath feel heavy and the air almost damp with cold. Traveling in such conditions can be quite challenging, as the moisture in the air makes the cold penetrate deeper, making it essential to dress warmly and stay active to ward off the chill.
In Alton 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 Alton, you can check the information here.
UV Risk Categories
Weather in Alton varies notably across the year, with each month offering distinct climate conditions. This page compares December’s weather to other months in Alton, focusing on differences in temperature, rainfall, humidity, and UV levels.
| Temperature | Precipitation | Humidity | UV | |
|---|---|---|---|---|
| January Weather | -6°C (21°F) | 26 mm (1.0 inches) | 80% | low |
| February Weather | -6°C (21°F) | 32 mm (1.3 inches) | 84% | moderate |
| March Weather | 2°C (36°F) | 72 mm (2.8 inches) | 75% | moderate |
| April Weather | 8°C (46°F) | 95 mm (3.7 inches) | 79% | very high |
| May Weather | 15°C (60°F) | 140 mm (5.5 inches) | 74% | very high |
| June Weather | 23°C (73°F) | 114 mm (4.5 inches) | 81% | extreme |
| July Weather | 24°C (76°F) | 72 mm (2.8 inches) | 82% | very high |
| August Weather | 22°C (72°F) | 100 mm (3.9 inches) | 80% | very high |
| September Weather | 19°C (66°F) | 101 mm (4.0 inches) | 75% | very high |
| October Weather | 9°C (49°F) | 82 mm (3.2 inches) | 77% | moderate |
| November Weather | 2°C (36°F) | 28 mm (1.1 inches) | 85% | moderate |
| December Weather | -3°C (27°F) | 39 mm (1.5 inches) | 83% | moderate |