With a population of around 10,200, Waterloo sits in Illinois, United States. The city operates in the Central Time Zone.
In 2025, Waterloo recorded an average annual temperature of 57°F — right at the 30-year normal of 57°F. The hottest day reached 95°F in August; the coldest was -1°F in February. Total precipitation was 43 inches (wetter than usual). The wettest month was April.
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