We did in Chicago today! Recorded our first official 90-deg high temp of 2023 at 1:34pm Tuesday afternoon. This first 90 comes 19-days later than a year ago when the first 90 at O’Hare occurred on May 11th (a day earlier, May 10, 2022 at Midway).

Air quality issues have arisen with an Illinois EPA Air Quality Alert in effect until midnight. The presence of scattered t-storm should allow increased mixing of air a modest decrease in sunshine Wednesday thus cutting down on the photochemical reactions which produce ozone as a by-product.

The same wide spread in Chicago area temps between the immediate lake shoreline, where mid afternoon temps have held to 60 at the Wilmette harbor buoy, 65 on the Lake Forest shoreline, 64 at the Waukegan Harbor buoy, 67 at Burns Harbor, IN, 66 at Michigan City and 71 at Ogden Dunes and 72 at Calumet Harbor represented the coolest area temps. The offshore Harrison-Dever Crib—3 miles off the North Side of Chicago report 61-deg a mid afternoon.

In stark contrast, inland mid afternoon temps hit 93 at Warrenville, Tinley Park, Poplar Grove and Peotone while readings of 91 were observed at Plainfield, Carol Stream, Kankakee, Geona City (McHenry Co), Hebron, IN and Pontiac and 90-deg temps were recorded at CRete, Naperville, Woodridge, Vaparaiso, IN, Bonfield, Malta (DeKalb County) and Elburn among others.

Bottom line—there was as much as a 33-deg spread from the immediate lakeshore areas and areas inland.

Humidity’s are to increase. A more southerly flow around the backside of Eastern U.S. high pressure is sending more humid Gulf air with 60-65-deg dew points into the Chicago area. This combined with a modest destabilization of the atmosphere produces buoyancy of the air—an environment in which some scattered though low coverage t-storm may “bubble up” in coming days,

The desperate lack of moisture evidenced by the paltry 0.42″ of rain in May—just 10% of the normal tally and the 2nd least on record in any May over 153 years of official Chicago weather observations—is unlikely to be greatly affected by any isolated t-storms which occur in coming days. Still—rain is rain—and in the few areas which see some, it will be welcome. There are signs a tightening pressure gradient which is to drive a better organized easterly flow Friday and over the coming weekend is likely to force any t-storm development out of the Chicago area by stabilizing the atmosphere with better established and cooler winds off the lake.

Fact is, however, there are no widespread soaking rains showing up on model projections at this point. If such rains are out there, they’ve escaped the notice of numerical forecast models. IN fact, a projection of the potential % of normal precipitation which may occur over the next 2 weeks is put at 33%–hardly encouraging.

Lake breezes will continue cooling beach and lakeshore areas through the weekend. A better organized “NNE” flow appears a distinct possibly starting Monday night and/or Tuesday next week. That could will lead to a period of reduced temps and significant drying of the air as a flow from Canada becomes established. But there are hints a temp rebound may follow such a cooldown late in the two week forecast period ahead of us.

Of course, Thursday marks June’s arrival and our longest day in the northern hemisphere—June 21st—the astronomical start of summer 2023 is now just 23 days away. At that point days stop lengthening. But not to worry. The warmest temps have historically lagged our longest day by about a month.


TONIGHT: Partly cloudy with higher humidity’s and therefore warm overnight low temps. Low 67.

WEDNESDAY THROUGH THURSDAY: Partly sunny, warm and moderately humid days with some haze and continuing daytime lake breezes along Lake Michigan. Widely spaced, low coverage t-storms may impact up to 20 or 30% of the area in the afternoon and early evening hours of Wednesday and Thursday. High Wednesday 91—but mid 60s to low 70s beaches and lakeshore. Low Wed night 66. High Thursday 91—but closer to 70 on area beaches.

FRIDAY: A good deal of sunshine—just some cottony summertime cumulus clouds. Continued quite warm—but with cooler lake breezes. High 90—but 60s to near 70 lakeshore.

SATURDAY & SUNDAY: Partly sunny, continued warm inland. Better organized east winds along Lake Michigan. High Saturday 87; Sunday’s high 86—but 60s near Lake Michigan.

MONDAY: Partly sunny and warmer. Lighter lake winds. High 85—70s lakeshore.

TUESDAY: Mostly cloudy, breezy and cooler. High 78—but low to mid 60s lakeshore.