Gillespie, IL Weather Forecast
Macoupin County, Illinois
Seven-day outlook
40–80°F across the weekThe week runs between 53° and 80°, with today the warmest day of it. There is no real trend across it: one day looks much like the next. Tuesday is the wettest day, peaking near 56%.
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 Gillespie forecast
Gillespie sits at 39.1254°N, 89.8173°W in Macoupin 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
- Macoupin County
- Coordinates
- 39.1254°N, 89.8173°W
- Population
- 3,112 · 2023 estimate
- Land area
- 1.484 sq mi
Place data from the US Census Bureau. Coordinates are the Census internal point for Gillespie, 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 Gillespie?
The nearest Doppler radar is KLSX (St. Louis, MO), 55 miles to the WSW. 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 Gillespie its center is about 4,100 ft above ground. That is far enough out that the beam has climbed above the lowest few thousand feet. Storm structure aloft is visible; a shallow circulation near the ground may not be, and a warning here can arrive before anything looks dramatic on the radar picture.
The closest instrument actually measuring the air is K3LF · Litchfield Muni on the ASOS/AWOS network, 8.0 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 Gillespie
- Staunton, IL8 mi
- Litchfield, IL9 mi
- Carlinville, IL11 mi
- Hillsboro, IL19 mi
- Bethalto, IL20 mi
- East Alton, IL23 mi
- Wood River, IL23 mi
- Alton, IL24 mi
Elsewhere in Illinois
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