textproduct: Central Illinois

KEY MESSAGES

- Hot and humid weather returns Tuesday through next weekend with maximum heat indices ranging from the upper 90s to around 100 degrees each afternoon.

DISCUSSION

Issued at 117 PM CDT Sun Jul 12 2026

Water vapor imagery early this afternoon shows an upper low spinning over the Ohio Valley region with high pressure centered over the Central High Plains. Widely scattered showers have developed within the vicinity of the low, with a low chance (<20%) for activity to stretch as far north as southeast Illinois (south of I-70) through the remainder of this afternoon. Gentle northeast winds will advect lower dewpoint air southward overnight, with lows expected to bottom out in the low to middle 60s.

Upper ridging dominates the central US this week as the previously mentioned low meanders westward, resulting in a rex block. Temperatures will steadily climb the next couple of days, becoming seasonably hot by Tuesday through next weekend. The ECMWF Extreme Forecast Index shows values between 0.9-1 through at least Saturday, which indicates that there is high confidence of an anomalous event. Dewpoints in the low to middle 70s will be a touch lower than our late June/early July heat wave, though with corn and soy plants at their peak for evapotranspiration, dewpoints may overperform. Peak heat indices look to top out in the upper 90s to near 100 with ensemble guidance showing at least a 20-30% chance for values to exceed 100 degrees each afternoon through next weekend.

Precipitation chances look minimal through next weekend as we remain shielded by high pressure ridging. Longer range guidance depicts a shortwave trough diving through the Great Lakes Region sometime late next weekend or early next week, which may bring low end chances for showers and storms along a cold front. However, discrepancies in timing, placement, and strength exist this far out.

AVIATION /00Z TAFS THROUGH 00Z TUESDAY/

Issued at 633 PM CDT Sun Jul 12 2026

VFR conditions will prevail at all TAF sites next 24hrs. Skies will be clear through the period and winds will be light out of the northeast.

ILX WATCHES/WARNINGS/ADVISORIES

None.