Johnsburg, IL Weather Forecast
McHenry County, Illinois
Seven-day outlook
39–67°F across the weekThe week runs between 40° and 66°, with today the warmest day of it. There is no real trend across it: one day looks much like the next. Saturday is the wettest day, peaking near 64%. 3 of the 7 days stay dry.
Forecasts come from the National Weather Service's own computer models, and current conditions from the nearest reporting weather station. Both are served through the weather API. A forecast is guidance, not a warning, and anything the Weather Service has actually issued is on the live map.
The written summaries on this page are generated from the forecast data above, not by a meteorologist. Each sentence is a reading of the same numbers you can see, and no forecaster has reviewed them.
About the Johnsburg forecast
Johnsburg sits at 42.3832°N, 88.2468°W in McHenry County, Illinois. The forecast above is drawn for that point from the National Weather Service's own computer models: a seven-day outlook, and a finer-grained one covering the next eighteen hours where it reaches, and the radar and alert panels show what the Weather Service has out over the area right now.
- County
- McHenry County
- Coordinates
- 42.3832°N, 88.2468°W
- Population
- 6,384 · 2023 estimate
- Land area
- 7.254 sq mi
Place data from the US Census Bureau. Coordinates are the Census internal point for Johnsburg, and the forecast is for that location, not for every address inside the city limits, and a large city can have real weather differences from one side to the other.
How well can the network see Johnsburg?
The nearest Doppler radar is KMKX (Milwaukee, WI), 43 miles to the NNW. A WSR-88D's lowest routine scan sits half a degree above horizontal, and the earth curves away beneath it, so by the time that beam reaches Johnsburg its center is about 2,900 ft above ground. That is comfortably inside the useful range. The lowest scan passes low enough over Johnsburg to show rotation in the part of a storm where tornadoes actually form. Johnsburg is closer to its radar than 51% of US cities.
The closest instrument actually measuring the air is KUGN · Waukegan Rgnl on the ASOS/AWOS network, 20 miles away. Far enough that "current conditions" for Johnsburg is an educated reading of somewhere else, worth knowing before you plan around a single temperature.
Beam height is the standard 4/3-earth approximation for the 0.5° scan and assumes normal refraction; it is where the center of the beam is, not its edges, and unusual temperature profiles bend it. Radar siting from the NWS WSR-88D network, station positions from the Illinois observing network as of this build.
Forecasts near Johnsburg
- Lakemoor, IL4 mi
- McHenry, IL4 mi
- Fox Lake, IL4 mi
- Spring Grove, IL5 mi
- Wonder Lake, IL5 mi
- Volo, IL6 mi
- Round Lake Heights, IL7 mi
- Island Lake, IL8 mi
Elsewhere in Illinois
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