textproduct: Central Illinois

KEY MESSAGES

- Expect comfortable weather with low humidity and below-normal highs in the low-to-mid 80s through Tuesday.

- Widespread showers and thunderstorms are likely (60-90% chance) late Wednesday night through Thursday as a front passes. SPC has introduced a marginal risk (level 1 of 5) for severe weather on Wednesday.

- High confidence remains for building high pressure and a return to dry conditions with highs near 90F by next weekend. There is a 40-60% chance for heat indices greater than 95 degrees on Monday afternoon across the entire forecast area.

DISCUSSION

Issued at 232 AM CDT Mon Aug 3 2026

Dry weather is expected through Tuesday night as a high pressure lingers over the region. Highs in the 80s and low in the 60s will be in place for the week. Temperatures look to approach 90 degrees for highs by Sunday and Monday, with increasing humidity throughout the week. The LREF shows a 20-40% chance of apparent temperatures being greater than 95 degrees on Sunday afternoon and 40-60% chance on Monday afternoon across the entire forecast area. The CPC has both the 6-10 and 8-14 day outlooks with 60-70% chance of above normal temperatures, so the sweltering weather isn't over quite yet for this summer.

A more active pattern will return Wednesday as the upper flow gets disturbed by a 500 mb short wave that will push a cold front into the state. The latest global models (GFS, Euro) are showing an area of showers scraping the northern edge of our forecast area overnight Tuesday. Then, they are showing the main complex of convection Wednesday afternoon/evening moving north of a McDonough County to McLean County line with additional showery activity south of there overnight into Thursday. Although, the exact location may continue to shift as we approach midweek. There is no shortage of CAPE Wednesday afternoon, with MUCAPE values (and similarly SBCAPE values) around 1500-2500 J/kg and bulk shear values of 30-50 knots. SRH values look to be around 200-300 in the vicinity of the complex. This should sufficiently support thunderstorm activity. We could see some severe weather on Wednesday afternoon, focused north of I-72, closer to I-74. The SPC has introduced a marginal risk for severe weather on D3 (Wednesday).

The front on Wednesday could possibly stall out over the area, bringing additional rounds of showers and thunderstorms into the weekend next week. However, latest runs of the global models are depicting more of a dry pattern for later in the week into the weekend. We will continue to monitor the shower and thunderstorm possibilities beyond Thursday morning as we move forward in the week.

AVIATION /06Z TAFS THROUGH 06Z TUESDAY/

Issued at 1220 AM CDT Mon Aug 3 2026

High pressure will continue to slowly meander over Illinois over the forecast period, bringing mostly clear skies, but also an opportunity for fog to develop overnight. Have included MVFR vsby by 08Z-09Z, and tempo for IFR vsby from 09Z-12Z, although more dense fog is possible and will be monitored for. Winds light and variable through the period.

ILX WATCHES/WARNINGS/ADVISORIES

None.