Belvidere, IL Weather Forecast
Boone County, Illinois
Seven-day outlook
39–67°F across the weekThe week runs between 39° and 67°, with Tuesday 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 68%.
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 Belvidere forecast
Belvidere sits at 42.2654°N, 88.8878°W in Boone 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
- Boone County
- Coordinates
- 42.2654°N, 88.8878°W
- Population
- 25,297 · 2023 estimate
- Land area
- 12.514 sq mi
Place data from the US Census Bureau. Coordinates are the Census internal point for Belvidere, 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 Belvidere?
The nearest Doppler radar is KMKX (Milwaukee, WI), 51 miles to the NNE. 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 Belvidere its center is about 3,700 ft above ground. That is comfortably inside the useful range. The lowest scan passes low enough over Belvidere to show rotation in the part of a storm where tornadoes actually form.
The closest instrument actually measuring the air is KRFD · Rockford Intl on the ASOS/AWOS network, 11 miles away. Near enough to be representative on most days, though a summer thunderstorm can soak one and miss the other entirely.
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 Belvidere
- Cherry Valley, IL5 mi
- Poplar Grove, IL6 mi
- Loves Park, IL8 mi
- Rockford, IL9 mi
- Machesney Park, IL10 mi
- Roscoe, IL13 mi
- Davis Junction, IL15 mi
- Marengo, IL15 mi
Elsewhere in Illinois
ChicagoAuroraJolietNapervilleRockfordElginAll Illinois forecasts →