textproduct: Central Illinois

KEY MESSAGES

- No significant weather is expected across central Illinois through early next week. Low chances of showers (20-30%) in southeast IL overnight Saturday night and Sunday.

- Due to dry fuels and low afternoon relative humidity values, there is an elevated risk for agricultural field fires through Saturday especially southeast of the IL river where afternoon humidity levels will likely reach 30% or less.

DISCUSSION

Issued at 315 AM CDT Tue Oct 6 2026

Large surface high pressure over southeast Ontario peninsula and eastern Great Lakes region was still ridging sw into central/se IL. Meanwhile a 999 mb low pressure over northern Manitoba Province has a frontal boundary extending through eastern ND, central SD and nw Nebraska. Nearby high pressure ridge continue clear skies with light to calm winds over central/se IL. Seasonably cool temperatures were in the mid to upper 40s, ranging from 42F at NWS office on east side of Lincoln to 50F at the Bloomington and Peoria airports. Very patchy shallow ground fog was near rivers/waterways with Robinson airport having dense fog (vsby less than 1/4 miles), and Jacksonville airport vsby 1.5 miles. Added patchy fog early this morning in southeast IL especially near the Wabash river valley and over the middle/lower IL river valley. HRRR model has been more aggressive than other CAMs with showing patchy dense fog in southeast IL (generally se of a Paris to Shelbyville line) drifting sw and lifting by 8 am.

High pressure to settle near the mid Atlantic coast by sunset while ridging into the mid MS river valley and continue ample sunshine over CWA again today. A cold front to push into southern WI and northern Iowa by sunrise Wed and into central IL during Wed afternoon. Will see light to calm winds early this morning becoming southerly and increase to a bit breezier levels by afternoon with gusts up to 20 mph north of I-72. Mild highs today in the mid to upper 70s, warmest from Springfield sw. Fair tonight with some increasing high clouds from the nw, with lows in the low to mid 50s. Cooler lows in the upper 40s near the Wabash river valley where patchy shallow ground fog could develop overnight, with upper 50s over west central IL near MS river valley. SW winds 5-15 mph Wed morning to turn west to nw during Wed afternoon as weak cold front passes through dry. Warm highs in the low to mid 80s on Wed, warmest from I-72 south.

Weak 1020 mb high pressure settles se into the Midwest and IL during Thu with north to nw winds around 10 mph or less and mostly sunny skies. Highs Thu range from the lower 70s from Canton to Normal north with upper 70s to around 80F from Springfield and Paris south. High pressure strengthens as it settles eastward over the mid Atlantic States on Friday with return light SE flow setting up over IL. Temps on Friday near or just above Thursday's levels in mid 70s to around 80F. Warmer highs in the low to mid 80s on Saturday as strong mid/upper level ridge builds into IL and southerly flow increases.

The National hurricane Center (NHC) has an 80% chance of a tropical cyclone development next 48 hours over the sw Gulf of America. This system will likely spread deeper gulf moisture northward across the Southeast States during this weekend as low pressure lifts into the lower MS river valley during Sat night. Big question will be how far north it is able to spread its moisture into IL and current NBM keep 20-30% pops in southeast IL overnight Sat night into Sunday. The earlier runs of the extended models mostly brushed se IL with some qpf overnight Sat night and Sunday with heavier qpf and stronger winds from Ohio river se. Latest Ecmwf has shift low track northward to near Paducah by midday Sunday with qpf overspreading much of CWA during overnight Sat night into Sunday while GFS and GEM models keep brunt of QPF se of CWA. We need to monitor this tropical system. Temps to likely be cooler Sunday with more clouds and possible showers around especially in southeast IL. Extended models build another strong mid/upper level ridge into IL early next work week with warm temps likely Mon/Tue

AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/

Issued at 533 AM CDT Tue Oct 6 2026

VFR conditions are forecast to continue across the central IL airfields through 12Z/7 am Wed. Fair wx compliments of large high pressure over the eastern Great Lakes and upper Ohio river valley drifting toward the mid Atlantic Coast this evening and ridging back into the mid MS river valley. Light to calm winds at dawn to become southerly and increase to 7-11 kts by 14-16Z with few gusts 14-18 kts this afternoon. SSW winds 5-8 kts expected tonight starting around sunset. Few mid/high clouds could move in overnight.

FIRE WEATHER

Issued at 343 AM CDT Tue Oct 6 2026

Given the prolonged stretch of dry weather especially south of I-72, and RH values routinely dropping to 30% or less southeast of the IL river during the afternoons especially today and Thursday through Saturday, a heightened risk for agricultural field fires exists through Saturday. Though fairly light ambient winds this week will limit widespread fire weather concerns. Boundary layer moisture will be on the increase by Sunday as tropical moisture flows northward from the Gulf of America, and this should lessen fire wx concerns. Around 36% of corn and 31% of soybeans have been harvested in Illinois as of Oct 4th and we are in peak harvest season during the month of October.

ILX WATCHES/WARNINGS/ADVISORIES

None.