textproduct: Central Illinois

KEY MESSAGES

- Seasonal, low-impact weather is expected through today.

- Showers and storms return Wednesday. Some of these storms could be strong to severe, with damaging winds and large hail being the primary hazards.

- Summer-like heat returns later this weekend into early next week. There is a 40-60% chance temperatures exceed 90 degrees Sunday afternoon south of a Springfield to Effingham line.

DISCUSSION

Issued at 232 AM CDT Tue Aug 25 2026

~1019 mb surface high pressure is centered over northern Indiana early this morning, with surface ridging extending westward into the Middle Mississippi Valley. Light winds and mostly clear skies have allowed temperatures to drop into the upper 50s to low 60s this morning. Tranquil weather is expected to continue through today, with high temperatures topping out in the upper 70s to low 80s. Increasing cloud cover ahead of an approaching cold front will keep temperatures a little warmer tonight, in the low to middle 60s.

A mid-level shortwave will track through the southern Canadian Prairies and into the northern Great Lakes Region on Wednesday, sending a cold front through Illinois. Out ahead of the front, temperatures will climb well into the 80s with low 70s dewpoints expected to pool ahead of the front. By mid to late afternoon, CAMs show a broken line of supercell thunderstorms developing in a moderately unstable airmass with SBCAPE up around 2000-2500 J/kg and 30 kts of wind shear. Although the better forcing will be displaced to our north closer to the shortwave, a few strong to severe storms could develop from late Wednesday afternoon and evening, posing a threat for damaging wind gusts and isolated large hail. Modest directional shear noted in forecast hodographs may be enough to support a brief tornado or two.

Northwest flow aloft remains in place through late this week, which will ultimately keep things relatively dry and pleasant with temperatures near our seasonal normals. Upper ridging will begin shifting east this weekend, raising mid-level heights locally and bringing the return of summer-like heat. Temperatures look to climb into the upper 80s to low 90s, with the NBM indicating favorable probabilities (40-60%+) for temperatures over 90 degrees south of a Springfield to Effingham line on Sunday and a tier or two of counties north of there on Monday. Precipitation chances late this weekend into early next week look to remain confined over the northern half of the state with the upper ridge preventing any frontal systems from intruding too far south.

AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/

Issued at 526 AM CDT Tue Aug 25 2026

Light winds under surface high pressure may result in a brief period of patchy MVFR fog at the start of the TAF period. The surface high will shift east of here today, with winds becoming southeasterly by midday then southerly later tonight. FEW to SCT high based diurnal cumulus will develop later this morning with a thicker mid-level deck spreading in overnight ahead of an approaching front.

ILX WATCHES/WARNINGS/ADVISORIES

None.