textproduct: Chicago

KEY MESSAGES

- Seasonably warm conditions today and Monday, although cooler and more comfortable than recent days.

DISCUSSION

Issued at 220 AM CDT Sun Sep 6 2026

Conditions are nice and quiet out there this morning as we're off to a mild start to our Sunday. Relatively cooler, but still seasonably warm, weather is in store for today following a stretch a hot, humid conditions. High temperatures are forecast in the lower 80s today away from the lake and middle to upper 70s closer to the lakeshore. Dewpoints are still hanging out in the upper 60s this morning, but steady dry advection from high pressure building in from the northeast should pull dews down into the upper 50s by late this afternoon. This means we're not looking at much of a heat index factor today and conditions should feel close to what the thermometer reads.

Breezy ENE winds over the lake have gradually been subsiding through the night and waves have responded similarly. Moderate wave action will likely be present at Illinois beaches through the morning which could make swimming hazardous for those who aren't strong swimmers. So we're advertising a Moderate Swim Risk to start the day at Illinois beaches, although conditions will be easing through the day. Conditions look generally favorable for Labor Day tomorrow, but keep in mind high temperatures are forecast in the 70s both today and tomorrow along the lakeshore, maybe close to 80 tomorrow at Indiana beaches.

Similar to today, temperatures for Labor Day are forecast in the lower 80s away from the lake. High pressure over the northern Great Lakes will keep rain chances away and bring mostly sunny skies.

During the middle of the week, a tighly-wound upper low will track east across Ontario and a cold front will get dragged across the area sometime Wednesday bringing our next opportunity for rain and thunderstorms. Temperatures should trend up again beginning on Tuesday in anticipation of this system with highs forecast in the middle and upper 80s on Tuesday and Wednesday. There remains a great deal of uncertainty regarding this system from the timing of the frontal passage to the ambient environment near the front. Lapse rates aloft look generally poor as the cooler mid level air looks to stay wrapped up in the upper low to the north, and a prominent high across the SE US may also impinge on low level moisture feed ahead of the front further constraining instability. There will also be a diurnal factor to consider but is not yet clear. Considerable spread exists even within individual ensemble system regarding the thermodynamic environment. The Euro and GFS also have quite different ideas on the kinematic environment around the front, so it's unclear what quality of shear or kinematic forcing we'll have to work with, but the more supportive shear should also focus to our north near the base of the upper low. The more bullish scenarios do support a marginal severe threat for Wednesday, so something to keep an eye on over the next few days.

The main upper trough axis will swing over early Thursday and drive a secondary cold front across the area, but layer moisture looks to get shunted to our south after Wednesday and precip potential currently looks low during the day on Thursday. Behind the departing trough, a series of shortwave impulses traversing a generally zonal upper flow pattern will drive sporadic rain chances through next weekend with a larger synoptic system favored by medium range guidance to traverse the region in the late Sunday-Monday window.

Doom

AVIATION /18Z TAFS THROUGH 00Z TUESDAY/

Issued at 1216 PM CDT Sun Sep 6 2026

High pressure across the Great Lakes region will lead to VFR conditions with passing cirrus and limited diurnal cumulus. ENE/NE winds at 10 to 15 knots this afternoon will diminish to under 10 knots tonight, then veer E/ESE up to 10 knots on Monday.

Kluber

LOT WATCHES/WARNINGS/ADVISORIES

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