Illinois, United States of America · population 73,254 · 289 weather stations within 200 km · records 1777 to 2025
Decatur has an average annual daytime high of 17.2°C, based on the 1951 to 1980 baseline. Its warmest month is July, when highs typically reach 30.4°C, and its coldest is January, with overnight lows near -8.6°C.
These figures reflect annual averages, not single-day records. Daily observations are outside this dataset's precision.
Since 1900, Decatur's average temperature has risen by +2.1°C. Compared to the earliest station records that begin in 1777, warming totals +2.3°C.
20-year smoothed annual temperature reconstructed from station anomalies. Dashed line: 1951–1980 baseline.
Daytime highs sit within a comfortable 15°C to 26°C range.
Decatur's average annual daytime high is 17.2°C, based on the 1951 to 1980 baseline period. The warmest month is July, with highs averaging 30.4°C, and the coldest is January, with lows averaging -8.6°C.
July is the warmest month in Decatur, with typical daytime highs of 30.4°C.
2011 is the hottest year on record for Decatur, running +2.7°C above the 1951 to 1980 baseline.
Yes. Since 1900, Decatur has warmed by roughly +2.1°C.
April to October typically offers the most comfortable daytime highs, in the 15°C to 26°C range.
Baseline period 1951 to 1980. Monthly averages are the mean of station observations weighted by proximity. Warming trend is the 20-year smoothed anomaly against that baseline.