Sumner, IL 62466 Weather

Key Messages

- Dry conditions and tranquil weather to prevail across central and southeast Illinois through Monday.

- Above normal temperatures will dominate the region today through Monday, with afternoon highs climbing into the 70s.

Discussion

Issued at 300 AM CDT Wed Oct 21 2026

The nice fall weather looks to continue through Monday across central and southeast IL, favorable weather for harvesting and outdoor activities.

The 08Z/3 am surface map shows 1032 mb high pressure over the southern Quebec Province and ridging sw into IL/IN. Aloft there is an upper level ridge over the nations mid section with cutoff low/trofs off the mid Atlantic/New England coast and off the California coast. A weak short wave trof was over the Central Plains in central KS and producing isolated to scattered showers over the Central Plains, as far east as far western MO and far sw Iowa. Broken to overcast mid/high clouds were spreading into sw Iowa and central/western MO while nearly clear skies prevail over IL. Some patchy shallow ground fog over far eastern IL near Wabash and Kankakee river valleys and over Shawnee National forest in southern IL. Patchy fog over far eastern/se CWA to lift quickly by mid morning. Temps were mostly in the 40s over CWA, but as cool as 39F at NWS Lincoln and Robinson, with BMI the milder spot at 49F.

The short wave trof over the Central Plains will weaken as it moves over the MO valley today, spreading some mid/high clouds eastward into mainly western/sw CWA today with a fair amount of sunshine overall today especially in eastern IL. Surface high pressure ridge remains over IL keeping light to calm winds along with dry low levels. Highs today in the low to mid 70s which is about 10 degrees warmer than normal. Fair skies tonight with lows in the mid to upper 40s. 1030 mb or stronger high pressure over western Quebec and ridging into IL on Thu to continue ample sunshine with light ne winds and highs in the mid 70s. Light SE flow on Friday with a fair amount of sunshine and highs in the low to mid 70s (coolest near the Indiana border).

Medium range models continue to build a strong 500 mb ridge into IL Fri/Sat as 500 mb heights rise to 588 decameters or higher by Sat afternoon. SSE winds Saturday and more SW on Sunday but still fairly light flow especially Sunday. Skies become partly sunny over central IL during Sat with mostly sunny skies in SE IL and highs in the mid 70s (upper 70s from SPI sw). Partly cloudy skies prevail Sat night through Monday overall. Highs 75-80F on Sunday and low to mid 70s Monday.

Forecast models diverge with upper level trof moving into the Central Plains on Monday and pushing a frontal boundary se into IL Monday night into Tue. This could bring our next chance of showers to the area overnight Mon night into Tue, though NBM pops are currently 20% or less and mainly on Tuesday. Strong upper level ridge over the Southeast States early next work week could slow this frontal boundary and also return gulf flow limited by surface high pressure over mid Atlantic and gulf coast states. Temperatures to cool closer to normal for middle of next week starting on Tuesday. A stronger system appears to bring a better chance of showers to IL middle of next week around Wed night and Thu with temperatures cooling further.

Aviation

Issued at 608 AM CDT Wed Oct 21 2026

VFR conditions will prevail at all TAF sites next 24hrs with clear skies. Winds will remain light and variable.

Ilx Watches

None.