textproduct: Central Illinois

KEY MESSAGES

- A Frost Advisory is in effect this morning along and west of a Lacon...to Lincoln...to Taylorville line.

- Frost will be likely across areas generally east of I-55 tonight. Sensitive outdoor plants need to be protected this weekend in order to avoid damage.

DISCUSSION

Issued at 143 AM CDT Sat Oct 17 2026

The large eastern US trough is approaching the eastern seaboard this morning with NNW flow aloft in its wake. At the surface, high pressure is centered over the central and southern High Plains with a ridge axis extending northeast through IA/WI/MI. A few lake effect showers will persist along the IL/IN border early this morning, mainly bringing a few clouds to eastern central IL this morning. The surface ridge axis will drift southeast today with the high actually shifting east to the OH River Valley tonight. Expect light winds, clear skies and the potential for frost tonight. After highs in the upper 50s or so today, temps will fall through the 50s and 40s tonight. The winds will be the limiting factor, keeping temps up a bit in the western zones. However, expecting temps to be in the 33 to 36 degree range generally east of I-55 late tonight. In McLean Co, Bloomington/Normal may not cool enough for frost due to its higher elevation (it might be more patchy), but areas east of the cities will likely see areas of frost. The further west you go, frost will be more patchy and limited to valleys and areas where the wind can decrease. A Frost Advisory has been issued for tonight generally east of I-55.

On Sunday, we'll pass through "normal" with highs rebounding closer to normal/average for this time of year...the mid 60s. Sunday night the surface ridge axis will extend westward from OH through IN to IL. So, we will likely have some rather light winds. However our low level temps will have warmed a bit, so frost shouldn't be as likely as it is tonight. Still, it might be close and patchy in some areas of east-central IL. For Monday through Friday, Illinois will see highs rise through the 70s to around 80 with lows rising from around 40 to around 50. With average highs in the mid 60s for this time of year, being 15 degrees above average will be rather significant. By the weekend, we'll see a system approaching with highs likely peaking in the low 80s for Saturday, followed by a cold front and a chance for showers Sunday night.

AVIATION /12Z TAFS THROUGH 12Z SUNDAY/

Issued at 552 AM CDT Sat Oct 17 2026

TAFs for the next 24 hours reflect VFR conditions and the expected light winds across central Illinois.

ILX WATCHES/WARNINGS/ADVISORIES

Frost Advisory until 9 AM CDT this morning for ILZ027>031-036- 037-040>042-047>052. Frost Advisory from 1 AM to 9 AM CDT Sunday for ILZ038-043>046- 052>057-061>063-066>068-071>073.