textproduct: Central Illinois

KEY MESSAGES

- Temperatures will cool into the mid 30s to lower 40s early this morning, coolest near the Indiana border where frost is more likely. Continue to take precautions to protect sensitive vegetation with these colder temperatures and threat of frost over eastern IL early this morning.

- Dry and mild weather is expected this week along with a fair amount of sunshine and fairly light winds. Highs today and Tuesday in the lower 70s, will climb into the mid to upper 70s Thursday through Sunday. Areas from Springfield southwest have a 20-30% chance of nearing 80 degrees this weekend.

DISCUSSION

Issued at 330 AM CDT Mon Oct 19 2026

The 08Z/3 am surface analysis shows expansive 1034 mb high pressure over the upper Ohio river valley (northeast WV) and ridging sw across the Ohio river valley and into the mid MS river valley. Large high pressure continued clear skies across IL early this morning, with light SSE to calm winds. Seasonably cool temps ranged from 35-45F with mid 30s from Paris to Robinson, while NWS on east side of Lincoln was down to 34F. A frontal boundary was over nw WI into southern MN, central Nebraska to 1011 mb low pressure along the southern CO/KS border.

Another high pressure system builds over the Great Lakes region by days end, while frontal boundary stays well north/nw of IL, while mid/upper level ridge into IL keeping us dry and the front well to the north. Patchy frost possible east of I-55 until around 8 am, then a delightful fall day ahead with some cirrus clouds to spread eastward over central IL during this afternoon/evening. Though still ample sunshine today with light south winds. Highs today around 70F to lower 70s and dry dewpoints in the mid 30s to lower 40s. Good radiational cooling will be in place again tonight with fair skies, light winds and low dewpoints. Lows mostly in the lower 40s overnight with some upper 30s near the Indiana border. High pressure drifting over Quebec by sunset Tue while ridging sw across the Great Lakes and into IL will provide a fair amount of sunshine Tue with light east/se winds and a bit milder highs 70-75F. Lows Tue night in the low to mid 40s. Large high pressure over southeast Canada and New England Wed is ridging back into IL yet and provides sunshine with light to calm winds and highs in the low to mid 70s. Ample sunshine and light winds again Thu with nearby high pressure ridge and highs in the 70s.

A blocking upper level pattern over the US this week with upper level lows/storm systems off the East Coast and the CA coast with upper level ridging in nations mid section including IL. The upper level ridge builds over IL late this week with a bit warmer temps in mid to upper 70s Thu thru Sunday. Areas from Springfield sw have a 20-30% chance of reaching near 80F this weekend. A stronger storm system moves across southern Canada this weekend but consensus of models keeps qpf north and west of IL through early next week as above normal temperatures continue.

The Climate Prediction Center 6-10 Day Outlook for Oct 24-28 has 65-75% chance of above normal temperatures over IL, while 40-50% chance of below normal precipitation in central IL and 50-55% chance below normal precipitation in southeast IL. So this weather pattern next two weeks looks good for the fall harvest of corn and soybeans in IL which is running ahead of schedule. CPC 8-14 Day Outlook for Oct 26-Nov 1 continues 65-75% chance of above normal temperatures over IL while precipitation trending near normal in eastern IL and slightly above normal (~35%) over western half of IL.

AVIATION /12Z TAFS THROUGH 12Z TUESDAY/

Issued at 626 AM CDT Mon Oct 19 2026

VFR conditions will prevail at all TAF sites next 24hrs with clear skies and light and variable winds through the period.

ILX WATCHES/WARNINGS/ADVISORIES

None.