textproduct: Central Illinois

KEY MESSAGES

- There is a chance of showers over central IL on Friday especially Friday afternoon and evening, with more widespread showers and isolated thunderstorms on Friday over southeast IL. Between a quarter and half inch of rain is possible over southeast IL with lesser amounts in central IL. - Temperatures will gradually warm during this holiday weekend. Summerlike heat and humidity returns by the middle of next week as temperatures climb into the mid to upper 80s. There will be periodic chances of showers and thunderstorms during early and middle part of next week. Risk of severe storms appears low over central and southeast IL through the middle of next week.

DISCUSSION

Issued at 245 PM CDT Thu May 21 2026

Broken to overcast 3-5k ft clouds continue to slowly spread nw into central IL, reaching areas just se of I-55 at mid afternoon. Scattered to broken 4.5-9k ft clouds were over the IL river valley in nw CWA. A frontal boundary was draped across the Gulf Coast States with a surface trof over mid TN and southeast KY. Meanwhile a 1032 mb high pressure was over eastern Lake Superior into northern Lake Huron and ridging into IA and central/northern parts of IL. Breezy ENE winds over central IL with gusts 20-30 mph. Temps were in the upper 60s/lower 70s in central IL and mid 60s in cloudier areas from Litchfield to Charleston/Mattoon and Paris southeast.

Latest CAMs have wx system ejecting ne into the mid MS river valley by sunset Friday, and into the central Ohio river valley by sunrise Saturday. This system to spread scattered showers up into central and southeast IL, especially by Fri afternoon and better coverage in southeast IL where isolated thunderstorms are possible (though subsevere levels). Breezy ENE flow continues Friday and rainfall amounts appear lighter than previous runs with quarter to half inch in se IL and less than quarter inch in central IL and some spots less than a tenth inch especially from I-55 nw. Showers to diminish from the west during Friday night though isolated showers could linger into Sat morning.

Another disturbances brings another chance of showers and isolated thunderstorms on Sunday and from I-72 south on Monday/Memorial Day. A RexBlock pattern over the country during next week keeps a frontal boundary near the Ohio river and will see periodic chances of showers/thunderstorms during middle of next week. SPC severe wx outlooks along CIPS and CSU keeps risk of severe storms south of IL through next Thu night.

As for temperatures, not as cool tonight as last night, with lows in the low to mid 50s. Highs Friday in the upper 60s/lower 70s, warm into the mid to upper 70s Saturday, upper 70s/lower 80s Sunday and low to mid 80s Monday-Thursday, with increased humidity as the week progresses and dewpoints rise into the mid to upper 60s during mid week.

AVIATION /00Z TAFS THROUGH 00Z SATURDAY/

Issued at 550 PM CDT Thu May 21 2026

A stratocu deck with bases at 3-5k feet has been spreading northwest this afternoon and has now advanced west of I-55. This trend will continue overnight, with a low probability (less than 20%) that a terminal will drop to MVFR ceilings. Low level moisture increases from the south Friday morning, so we expect MVFR ceilings to develop north to the KSPI-KDEC-KSPI corridor by mid morning. Guidance shows a slow advance north of the MVFR deck through afternoon, so kept mention out of KPIA-KBMI for now. A few afternoon -SHRA will develop over eastern IL and mentioned VCSH at KDEC-KCMI only. Winds are forecast to be steady through the period, east at 10-15 kt.

ILX WATCHES/WARNINGS/ADVISORIES

None.