textproduct: Central Illinois

KEY MESSAGES

- Hot and humid weather with peak afternoon heat index readings of 100 to 110 will continue through Friday, and will likely reach 100 to 105 on Saturday afternoon, highest in southeast IL. An Extreme Heat Warning is in effect for central and southeast IL through 7 pm Friday.

- A low risk for severe weather exists both Friday and Saturday. The highest probability (15-30% chance) for scattered damaging wind gusts will focus along/north of a Peoria to Pontiac line Friday afternoon and evening.

- There is a Marginal Risk (5-15% chance) for excessive rainfall with some of the thunderstorms this weekend, particularly on Saturday.

DISCUSSION

Issued at 245 PM CDT Thu Jul 2 2026

**** Heat and Humidity ****

Dangerously high Heat Index readings will peak from 100-110 degrees during the afternoon and early evening hours today and Friday, highest along/south of the I-72 corridor where a few spots could top 110F for heat indices. Increasing cloud cover and thunderstorm chances will lead to a gradual easing of the heat over the holiday weekend, though we will likely see heat indices peak from 100-105 on Saturday afternoon and further heat headlines may be needed then. We continue messaging heat safety for central and southeast IL from this week long heat wave.

**** Severe Weather Risk Friday and Saturday along with heavy rains ****

Isolated showers and thunderstorms recently develop along I-55 in central IL including from Lincoln to just sw of Bloomington and drifting slowly ne. A few other cells had recently appeared near and just ne of I-74. Very unstable tropical airmass in place over CWA with MLCAPES 2500-4000 j/kg from IL river se while weak effective bulk shear values 20-25 kts. High PW values were 1.6-1.9 inches over CWA highest se of the IL river. The RRFS and HiRes ARW models picked up on this isolated convection this afternoon along I-55 and utilized it for near term forecast update this afternoon/early evening, with diurnally driven isolated convection to dissipate toward sunset. Could be some gusty winds and locally heavy rain with the stronger cells next few hours in heart of central IL.

More convection to develop and move into the nw CWA late evening and early overnight, getting about as far south as Peoria and then lift ne of CWA toward dawn. SPC Day1 outlook has marginal risk of severe storms with gusty winds far northern CWA (northern parts of Knox and Stark counties and far nw Marshall county). A disturbance over SD to track se over Iowa Fri morning and move into central IL during mid/late Fri afternoon and interact with lingering outflow boundaries from tonights convection. Best chance of convection Fri afternoon/evening to be north of I-72 where SPC Day2 has slight risk of severe storms from Canton to Bloomington north for mainly damaging winds. 5% risk of large hail along and nw of the IL river. Marginal risk of severe storms over rest of CWA Fri afternoon/evening. WPC day2 has marginal risk of excessive rainfall over northern IL and could see pockets of rainfall of 1-2 inches in 1-2 hours over northern CWA.

High chances of convection shift further south over CWA on Saturday into Sat night as cold front pushing down into northern IL Sat night. SPC Day 3 outlook has marginal risk of severe storms over CWA Sat afternoon/evening especially during peak heating from mid afternoon until sunset Sat with damaging winds and locally heavy rains main threat. WPC ERO has marginal risk of excessive rainfall across CWA both Saturday and Sunday, though heavier rain and stronger storm threat may shift further into southeast IL by Sunday afternoon as cold front pushes through CWA on Sunday.

Mid/upper level troffing digging into the Great Lakes early next week and moving into New England and mid Atlantic States by Tue to still keep daily chances of convection around though more widely scattered and diurnally favored in afternoon/early evening hours. Still warm and muggy Sunday through Wed, though temperatures and humidity levels trending closer to normal for early July levels. The Climate Prediction Center (CPC) 8-14 Day Outlook for July 10-16 has 35-40% chance of above normal temperatures over IL, while precipitation trending near normal in central IL and 33-40% above normal in southeast IL.

AVIATION /06Z TAFS THROUGH 06Z SATURDAY/

Issued at 1201 AM CDT Fri Jul 3 2026

Thunderstorms over northern Illinois have kicked out an outflow boundary south into portions of central Illinois. It is possible a few additional storms form along this boundary overnight, especially further north at PIA and possibly BMI, but confidence is too low to include mention in the TAF. Otherwise, light south winds and VFR conditions are expected to prevail overnight into most of Friday with winds veering to SW by late morning. Additional scattered showers and storms are expected to develop over central Illinois Friday evening. Low confidence in placement and expected isolated to scattered coverage precludes more than a prob30 mention at this time.

ILX WATCHES/WARNINGS/ADVISORIES

Extreme Heat Warning until 7 PM CDT this evening for ILZ027>031-036>038-040>057-061>063-066>068-071>073. Heat Advisory from 11 AM to 7 PM CDT Saturday for ILZ049>057- 061>063-066>068-071>073.