Johnson County weather, town by town
7 places in Johnson County, Illinois, each with its own live forecast and radar, and where a station sits close enough, measured weather records.
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Measured at the NOAA stations serving these towns, daily records 1895 to 2026. Station extremes, not official state records.
Johnson County Weather Facts
Johnson County has 7 places on myweatherrock (6 villages, 1 cities), each with its own live forecast, hourly timeline, ten day outlook and radar. The hottest day in the station records is 112°F at Anna 4 N on July 22, 1901. The coldest night is -20°F at Anna 4 N on January 12, 1918. The wettest day brought 7.74 inches of rain at Anna 4 N on March 18, 2008. The biggest single-day snow measured 20 inches at Anna 4 N on February 25, 1979. Those are station measurements from NOAA's daily records, 1895 to 2026, not official state records. By area the largest place is Vienna, about 3 square miles.
About Johnson County weather
The map on the Now tab shows every Johnson County town's current temperature from our own server, one dot per town. Tap any dot, or type a town above, for that town's full forecast.
What the weather is usually like
Across the 7 Johnson County towns with station normals, the warmest month is July, when the day usually reaches 89°F, and the coldest is January, when the night usually falls to 26°F. May is the wettest, with rain on about 10 days.
Means of the 1991 to 2020 station normals serving these towns, as published by NOAA; each town's page carries its own.
Where these numbers come from
- Current conditions and forecast: NOAA forecast grids decoded on our own server, corrected against the nearest reporting station and our own radar. Open-Meteo is consulted only as a fallback when our server is silent.
- Records: computed by myweatherrock from NOAA GHCN-Daily station records at the stations serving these towns. Measurements, not estimates.
- Warnings and alerts: the National Weather Service, passed through unchanged.
Johnson County weather records
Measured at the NOAA stations serving these towns, daily records 1895 to 2026. Station extremes, not official state records.
Common questions about Johnson County weather
- What is the hottest temperature recorded at a Johnson County station?
- 112°F at Anna 4 N on July 22, 1901, in the NOAA daily station records myweatherrock holds (1895 to 2026).
- What is the coldest temperature recorded at a Johnson County station?
- -20°F at Anna 4 N on January 12, 1918.
- What is the most rain a Johnson County station has measured in one day?
- 7.74 inches at Anna 4 N on March 18, 2008.
- What is the biggest one-day snowfall at a Johnson County station?
- 20 inches at Anna 4 N on February 25, 1979.
- How many Johnson County towns have a weather page here?
- 7: 6 villages, 1 cities. Each page carries current conditions, the hourly timeline, the ten day outlook, radar, and where a station sits close enough, measured records.
- Where does the Johnson County forecast come from?
- NOAA forecast grids (the National Weather Service digital forecast, the National Blend of Models, HRRR and GFS) decoded on our own server, corrected against the nearest reporting station and our own radar. Open-Meteo is consulted only as a fallback when our server is silent.
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