textproduct: Chicago

KEY MESSAGES

- Precipitation free, unseasonably warm weather will continue through this weekend, with temperatures continuing to generally run above average through next week.

- Chances for any meaningful rainfall are low through next workweek.

DISCUSSION

Issued at 150 PM CDT Fri Oct 23 2026

Tonight through Sunday:

As of this writing, what had been a bank of extensive fog and very low clouds across Chicago's far northern suburbs this morning has finally contracted to a remaining patch near Winthrop Harbor, IL. With lake enhanced moisture evident in the Waukegan and southeast WI dew point obs, wouldn't be surprised if patchy fog sneaks back into northeastern Lake County this evening from continued light to moderate southeasterly boundary layer flow.

Another calm night is in store tonight, with the main change happening aloft in terms of strengthening southerly flow just above the nocturnal inversion. Over the southeast half or third of the area (I-88 corridor in interior Chicago metro and points southeast), flow aloft should be sufficiently weak to enable patchy shallow ground fog development. Can't completely rule out very localized dense fog, but the setup isn't nearly as favorable as this (Friday) morning. High clouds will filter in from the northwest overnight into Saturday morning, keeping overnight lows a bit milder across interior northern Illinois in particular.

On Saturday, high temperatures will likely be close to a carbon copy of today (Friday), in the lower to mid 70s. Illinois side lake cooling will be confined to the immediate shoreline during the afternoon as southerly winds back to southeast with lake influence. Following a calm and cool (relative to Saturday afternoon's warmth) Saturday night, Sunday will likely be the warmest day of this stretch unless mid and high cloud cover limits high temps a bit.

Sunday Night through Friday:

A backdoor cold front will move across the area Sunday night, knocking temps down vs. the weekend for Monday's highs, but still above average for late October. The coolest readings (around 60F/low 60s) will be found near Lake Michigan due to strengthening north-northeast winds. Another period of well above average temps will follow through Wednesday or Thursday, followed by modest cooling to close out the week in the wake of a cold frontal passage. Chances for rain mid to late next week, while not zero, are low/nebulous, and the best chance for anything of note looks to be confined to well west and northwest of the local area.

Castro

AVIATION /18Z TAFS THROUGH 00Z SUNDAY/

Issued at 1247 PM CDT Fri Oct 23 2026

VFR conditions are currently forecast through the period. Patchy shallow fog can't be ruled out in low-lying and grassy areas outside of Chicago early Saturday morning, though the potential remains too low to include in the TAFs with this update.

Winds will remain light through tonight initially out of the SSE then turning E to ESE behind a weak lake breeze this afternoon (ENE at GYY). Occasional patches of VFR high clouds may drift through this evening and overnight with greater coverage expected Saturday morning. Winds also begin to turn SSE to S by mid-morning Saturday and increase to around 10 kt.

Petr

LOT WATCHES/WARNINGS/ADVISORIES

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