Vandalia, in Illinois, United States, is home to roughly 7,100 people in the Central Time Zone at 39°N latitude.
In 2025, Vandalia recorded an average annual temperature of 55°F. The hottest temperatures reached 94°F in September; the coolest were -2°F in January. Total precipitation for the year was 35 inches, with the wettest month being April. Snowfall for the year totaled approximately 8 inches.
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