textproduct: Central Illinois

KEY MESSAGES

- Hot and humid weather returns to central and southeast IL Tuesday through this weekend. Maximum heat indices to range from 95 to 105 degrees each afternoon Tuesday through Saturday with highs in the lower 90s common.

DISCUSSION

Issued at 145 AM CDT Mon Jul 13 2026

The 06Z/1 am surface map shows 1023 mb high pressure over southeast Iowa and northern MO and ridging over northern IL and southern lower MI. Meanwhile a weak 1016 mb low was in south central TN. Aloft a strong 600 decameter 500 mb high was along the eastern Dakotas border, while weak 588 decameter low was in southeast KY. Clear skies prevail across IL with light northeast to calm winds over CWA. Dewpoints were in the low to mid 60s while temps in mid to upper 60s central IL and lower 70s southeast IL. Very patchy shallow light fog was near the IN border with vsbys 5 miles Danville and 6 miles at Robinson.

The strong mid/upper level high pressure ridge over the upper Midwest will build eastward across the Great Lakes and into central/northern IL next few days, bringing in a heat wave to IL. Though this upcoming heat wave does not look as strong as the week long heat wave from Jun 28 to July 4th. Highs today in the upper 80s to near 90F, warmest from the IL river nw where heat indices this afternoon to peak in the mid 90s. The ECMWF Extreme Forecast Index shows values between 0.95-1 from Tuesday through Saturday, which indicates that there is high confidence of an anomalous event. Dewpoints in the lower to middle 70s overall during this heat wave, though mature corn and soybean plants to provide extra low level moisture from evapotranspiration, so dewpoints may overperform at times. Peak heat indices look to top out from 90 to 95 this afternoon and 95 to 105 degrees each afternoon from Tue through Saturday.

Precipitation chances continue to look slim over central/se IL through this weekend as we are influenced by strong mid/upper level high pressure ridge. A weak upper level low to drift westward over the southern TN river valley this evening, and into AR on Wed. We will likely be capped with nearby strong upper level high pressure just to our north/nw so continued a dry forecast into mid week. Most models keep convection south of CWA through mid week. GFS appears too far north and is an outlier with qpf into central IL on Wed. As the strong mid/upper level ridge retrogrades westward into the central Great Plains and Rockies late this week, with upper level troffing into the northeast quarter of the country, this may bring low end chances for showers and storms to IL this weekend. Though better chances of convection appears to be ne of central IL closer to the Great Lakes region with short waves track se through that part of the country with better forcing.

The Climate Prediction Center (CPC) 8-14 Day Outlook for July 20-26th is trending near normal for temperatures and precipitation over Illinois, except slightly above normal precipitation along the Indiana border. So overall a drier pattern likely in store for central and southeast next two weeks after a very wet period since Sun/Jun 7th when we received 7-14 inches of rain and a few spots over 15 inches.

AVIATION /12Z TAFS THROUGH 12Z TUESDAY/

Issued at 500 AM CDT Mon Jul 13 2026

Very patchy shallow ground fog near a some river valleys and lakes early this morning per Nighttime Microphysics satellite imagery. Brief IFR to MVFR vsbys with this fog may occur until 13Z, but kept out of central IL airports as chances for this is less than 20%. Otherwise VFR conditions are forecast to continue through 12Z/7 am Tue over central IL airfields with nearby surface high pressure ridge over southeast IA and northern parts of IL/MO. Few cumulus clouds with 5k ft bases may appear late morning/afternoon along with a few passing cirrus clouds. Light NNE to calm winds at dawn, to become NE at 5-10 kts after 15Z/10 am, and diminish light at sunset/01Z.

ILX WATCHES/WARNINGS/ADVISORIES

None.