textproduct: Chicago

KEY MESSAGES

- Record warmth is likely on Monday, along with breezy/gusty southwesterly winds.

- Showers likely and some embedded thunderstorms Tuesday night into Wednesday morning, and again on Thursday.

- Turning much cooler into next weekend.

DISCUSSION

Issued at 235 PM CDT Sun Oct 11 2026

Tonight through Tuesday:

Unseasonable warmth will continue to be the story for a few more days, particularly on Monday. Tonight, given dew points this afternoon in the mid to upper 50s in most spots, light southerly winds will enable overnight lows should to fall into the upper 50s to lower 60s (locally mid 50s) away from Chicago. These readings are still 10-15F above average for the date, providing a very mild starting point for Monday's warmth.

Some high cloud cover to start the day will give way to plenty of sunshine through the afternoon. Forecast soundings support southwesterly winds gusting up to 25 to 30 mph. With recent dryness and 925 mb temps in the lower to mid 20s Celsius, the setup looks prime for temps overperforming, reaching the mid to upper 80s. Record highs for October 12th are relatively low compared to surrounding days, making record highs a decent bet at Chicago and Rockford (see climate section below).

Can't completely rule out some high based sprinkles in spots on Monday night in advance of an approaching cold front trailing from surface low pressure over northern Lake Michigan by early Tuesday. The cold front will otherwise move across the area with little fanfare on Tuesday. Exceptionally mild conditions (60s to around 70F) to start Tuesday and very weak cold advection will result in another day of summer-like temps, though not quite as warm as those on Monday.

Tuesday Night through Sunday:

Anafrontal showers and some embedded thunderstorms are expected at times later Tuesday evening into Wednesday morning. This will occur as impulses riding fairly robust west-southwest mid-level flow interact with moisture and modest elevated instability atop the baroclinic zone over the region. There's some uncertainty with specifics in this period, including the potential for axes of higher QPF. All in all, the fairly high PoPs in the official forecast appear warranted. High pressure building down from the northern Great Lakes will shift showers primarily south of I-80 by mid Wednesday morning. Any additional afternoon showers will probably be confined to mainly south of the Illinois and Kankakee River Valleys (and perhaps even primarily south of US-24). Highs on Wednesday, while still above average for the date, will be noticeably cooler than Tuesday, particularly along the lakefront (mid-upper 60s) due to steady northeast winds.

The next period of interest for showers and embedded thunderstorms is on Thursday. While there is considerable variance in the evolution of key synoptic features on Thursday, including the track of weak surface low pressure, 60-70% PoPs in the official forecast appear reasonable. A strong cold front will sweep across the area Thursday night, with the coolest air mass of the season thus far moving in behind the front for Friday-Saturday. Seasonably strong (1030s to around 1040 mb) high pressure transiting the region may set the stage for areas of frost outside of Chicago Friday night into early Saturday and Saturday night into early Sunday, depending on how cool surface temps actually get. Expect temps to quickly moderate back to near seasonable Sunday afternoon.

Castro

AVIATION /06Z TAFS THROUGH 12Z TUESDAY/

Issued at 1240 AM CDT Mon Oct 12 2026

Forecast concerns for the terminals...

- Breezy southwest winds Monday afternoon with gusts peaking around 20-25 kts, locally higher gusts are possible.

- Potential for low-level wind shear Monday night if sufficient decoupling of winds can occur.

Mid-level ridging continues to reside over the Mississippi Valley and southern Great Lakes and is expected to remain in place through this TAF cycle. While a subtle disturbance is forecast to pivot along the northern periphery of the ridge Monday afternoon, guidance has continued to trend drier with any possible showers with this disturbance. Therefore, expect dry and FEW to SCT VFR skies to prevail through this TAF period.

Light south-southwest winds (around 4-5 kts) will persist tonight before winds become more southwesterly and increase in speed by midday Monday. Gusts Monday afternoon are expected to peak around 20-25 kts, but there is a chance (20-30%) for locally higher gusts near 28-30 kts after 20z. The gusts are expected to taper after sunset Monday evening, but with continued warm advection there is the chance for some occasional 18-20 kt gusts to linger through Monday night. However, if these occasional gusts do not materialize (ie the atmosphere decouples) then a threat for low-level wind shear could manifest after 03z as a strong 40-50 kt low-level jet develops overhead, especially at the outlying terminals. The current TAFs are favoring the breezier conditions lingering and thus have not included a formal LLWS mention but we will continue to monitor trends and adjust as needed.

Yack

CLIMATE

Issued at 235 PM CDT Sun Oct 11 2026

Here are the record warm temperatures most likely to be threatened or broken early this week.

Monday October 12th Record High Temps: Chicago's current record high: 84F in 2008 Rockford's current record high: 85F in 2008

Tuesday October 13th Record Highs Min Temps: Chicago's current record high min: 67F in 1920 Rockford's current record high min: 61F in 2008

NWS Chicago

LOT WATCHES/WARNINGS/ADVISORIES

IL...None. IN...None. LM...None.