textproduct: Chicago

KEY MESSAGES

- Generally warm conditions are expected through early next week but cooler near the lake Wednesday and again this weekend.

- Periodic shower and thunderstorm chances return Friday into early next week.

DISCUSSION

Issued at 259 PM CDT Tue Jun 2 2026

The quiescent weather pattern continues as an expansive 1030mb surface high remains centered over the Great Lakes. Northeast to east flow on the southern side of the high has helped keep temperatures cooler yet again today, with afternoon highs in the 60s along the lakeshore and 70s across the rest of northeast Illinois and far northwest Indiana. Areas west of I-39 and toward central Illinois still managed to reach the lower to mid 80s.

As the center of the surface high begins to gradually drift to the southeast into Wednesday the surface flow begins to trend more south to southeasterly here locally. The loss of broader lake influence will allow 80 degree temperatures to expand back into the majority of the area, the exception to this being along the lakeshore and a bit farther inland across far northeast Illinois. Temperatures may still manage to approach the lower 70s initially near the lakeshore toward midday given lighter flow in the morning before cooling back into the 60s in the wake of a reinforcing lake breeze in the afternoon. Breezy southwesterly warm air and moisture advection then sets up into Thursday through the end of the week allowing areas along the lakeshore to experience the warmer temperatures which are forecast into the low to mid 80s!

Ensemble guidance continues to point toward a more unsettled pattern returning toward the end of the week as the amplified upper ridge begins to break down. A series of shortwaves and associated surface fronts then likely traverse the broader region at times through early next week. The first of which is expected to arrive late Friday and could bring a period of scattered showers and storms. While the signal for severe weather is pretty low given overall weaker shear, anomalously high PWATs will be favorable for localized heavy downpours. Additional shower and storm chances exist Saturday and again early next week though there will still be plenty of dry hours.

The temperature forecast remains lower confidence this weekend into early next week and will ultimately be dependent upon shower and thunderstorm coverage along with the timing of any potential backdoor fronts. The general trend is toward onshore flow returning along with cooler conditions being favored near Lake Michigan Sunday into early next week.

Petr

AVIATION /00Z TAFS THROUGH 06Z THURSDAY/

Issued at 624 PM CDT Tue Jun 2 2026

No significant aviation forecast concerns with the 00Z TAF cycle.

Surface high pressure was centered over the western Great Lakes early this evening, maintaining modest northeast to east winds and fine VFR weather conditions across the terminals. Winds will gradually weaken after sunset, and are expected to become light and variable (less than 5 kts) overnight due to the proximity of the high pressure center. The high will begin to drift slowly off to the east of the area Wednesday, with winds becoming light south-southeasterly after sunrise. An east-southeasterly lake breeze (east-northeasterly at GYY) is expected to develop during the afternoon with a minor shift in wind direction to perhaps at 100-110 degrees at ORD/MDW. Winds Wednesday evening should become light south-southeast again. Otherwise, VFR conditions to persist with just a bit of an increase in high-level (~30 kft) cirrus.

Ratzer

LOT WATCHES/WARNINGS/ADVISORIES

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