textproduct: Central Illinois

KEY MESSAGES

- Hot and humid weather continues through at least Saturday with maximum afternoon heat indices between 95 and 100 degrees.

- Shower and storm chances return late this week with the best chances expected on Friday.

DISCUSSION

Issued at 1252 PM CDT Tue Jul 14 2026

Water vapor imagery shows a rex block in place over a good portion of the US -- upper ridging over the north-central CONUS and low pressure positioned equatorward of it. This has resulted in another period of seasonably warm temperatures and high dewpoints (low to middle 70s) leading to peak afternoon heat indices around 100 degrees, give or take a few degrees. Similar conditions are expected to last through at least the first half of the weekend, though the return of scattered convection later this week could alleviate the heat for some.

The upper ridge will begin to break down later this week as several shortwave troughs work through the eastern Canadian provinces, just north of the Great Lakes. The previously mentioned upper low will ooze northward in a weakened state beginning Thursday, bringing just enough forcing to support scattered storms through Saturday (Friday having the highest chances). With plenty of moisture in place, moderately strong instability could support a few stronger storms capable of gusty winds and torrential downpours. However, weak shear should limit storm longevity and organization.

Additional opportunities for showers and storms are forecast Sunday into early next week as a shortwave trough dives through the Great Lakes Region, sending a cold front south into the area. The front will stall out over central Illinois before lifting back north on Monday. Although a subtle reprieve from heat will come for some Sunday into Monday (northern counties), a more noticeable "cooldown" closer to our seasonal normals won't arrive until Tuesday when a stronger upper wave sends a more progressive cold front through the area. Normal high temperatures for the middle of July typically range from the middle to upper 80s.

AVIATION /06Z TAFS THROUGH 06Z THURSDAY/

Issued at 1154 PM CDT Tue Jul 14 2026

Calm winds and high boundary layer RH will bring patchy MVFR fog to the central IL terminals early this morning. High-res models show higher probabilities of IFR visibility at times near/west of I-55, but confidence of this impacting a terminal is low so kept out of TAF. Otherwise skies will be mostly clear and winds light/variable with high pressure overhead.

ILX WATCHES/WARNINGS/ADVISORIES

None.