textproduct: Central Illinois

KEY MESSAGES

- Hot and mostly dry weather is forecast this week with afternoon heat indices peaking above 100 degrees in west- central Illinois on Monday and areawide beginning Tuesday.

DISCUSSION

Issued at 120 PM CDT Sun Aug 30 2026

Radar mosaic has shown a persistent band of showers and isolated storms impacting areas north of a Macomb to Pontiac line most of the morning into early this afternoon. This activity has been fed by a 30-40 kt low-level positioned from central Kansas into northern Illinois and should come to an end here soon as the low-level jet continues to wane. Temperatures were reduced near/north of the I-74 corridor for today due to lingering precipitation and cloud cover, but areas south of there are already observing values in the upper 80s to low 90s as of 1 pm.

A ridge of high pressure centered over the Southern Plains will spread east this week, bringing a stretch of hot and mostly dry conditions. Temperatures this week will peak in the 90s with the hottest days expected by midweek. Dewpoints in the upper 60s to low 70s will send heat indices over 100 degrees as early as Monday in west-central Illinois and then areawide Tuesday, continuing through at least Thursday. High temperatures look to remain just shy of records at our official climate sites, but overnight lows in the mid 70s will likely tie or break our warmest low records.

A compact northern stream trough will track through the southern Canadian Prairies/Northern Plains this week, sparking occasional chances for showers and storms north of our area. The upper ridge will flatten out some late in the week as the trough tracks north of the Great Lakes Region, allowing shortwave energy to intrude further south. The NBM shows low chances for precipitation Thursday night through the start of the weekend before the ridge reamplifies later this weekend.

AVIATION /00Z TAFS THROUGH 00Z TUESDAY/

Issued at 605 PM CDT Sun Aug 30 2026

VFR conditions expected through the period, with mainly clouds near or above 15kft. Low level jet is expected to ramp up again across Iowa this evening, and edge eastward after 06z. Can't rule out the possibility of the fringes reaching KPIA, but the chances remain low enough to keep the mention of it out of the upcoming TAF set.

ILX WATCHES/WARNINGS/ADVISORIES

Heat Advisory from 1 PM to 7 PM CDT Monday for ILZ027-036-040- 041-047>052.