Is this weather normal in Johnson County?

Illinois · county records since 1895, through September 2026.

Weather › Illinois › Johnson County

Johnson County just had its warmest September ever recorded, +8° against the usual. Johnson County has warmed about 0.5° per decade since 1970.

This week

Usual for Oct 28 to Nov 3: highs near 63°, lows near 41°

That is the 1991 to 2020 average for these dates in Johnson County. The Weather Service forecast fills in below.

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usual high for the datewarmercooler

The last 12 months

Oct: +2.7°OctNov: +1.3°NovDec: +0.1°DecJan 2026: -3.2°JanFeb: +0.9°FebMar: +8.5°MarApr: +6.8°AprMay: -1.0°MayJun: -0.3°JunJul: +0.3°JulAug: +0.8°AugSep: +7.7°Sepwarmercooler

Each bar is a month's average temperature against the usual for that month (1991 to 2020). Ranks compare the same month in every year since 1895.

Every year since 1895

18952025

Rain and drought

Oct: +0.7 inOctNov: -2.1 inNovDec: -2.9 inDecJan 2026: -2.6 inJanFeb: -3.0 inFebMar: +0.6 inMarApr: -2.1 inAprMay: -2.3 inMayJun: +1.2 inJunJul: +3.6 inJulAug: +0.8 inAugSep: -2.1 inSepwetterdrier

Rain and melted snow against the usual for each month. The drought reading is NOAA's Palmer index for the county.

Month by month in Johnson County

MonthUsual high / lowUsual rainWarmestColdest
January42° / 26°3.6 in43.0° 200616.8° 1977
February47° / 29°3.5 in46.9° 201722.2° 1978
March57° / 37°4.7 in60.3° 201231.2° 1960
April69° / 46°5.3 in64.1° 202648.2° 1907
May77° / 56°5.1 in72.8° 196259.2° 1917
June85° / 64°4.5 in80.9° 195268.7° 1903
July88° / 68°4.3 in84.2° 190172.7° 2014
August87° / 66°3.2 in83.4° 193670.3° 1915
September81° / 58°3.4 in77.3° 202662.1° 1918
October70° / 47°3.8 in64.9° 196351.4° 1917
November56° / 37°4.4 in55.0° 190937.4° 1976
December46° / 29°4.0 in47.6° 202124.4° 1989

Warmest and coldest are the month's whole-month average temperature, with the year it happened.

Towns in Johnson County

Nearby counties