FROST ADVISORIES HAVE BEEN ISSUED FOR ALL BUT COOK AND LAKE COUNTIES ILLINOIS in Illinois and LaPorte county Indiana late tonight through 8am TUESDAY
Much of the Chicago area is headed for its chilliest night of the season and likely the coldest night at O’Hare—site of the city’s official thermometer reading—with a low near 39—the lowest temp here since 38 back on May 3rd this past spring.
Inland temps may drop to around 30 at a few of the coldest spots well away from the city.
The chill follows a weekend which came in 22-deg cooler than the weekend before and overnight temps this morning which were the lowest of the season to date and included readings as low as 32-deg at Livingston county’s Odell; 33 -deg at Waukegan; and 34 deg at Sugar Grove and at Johnsburg (in McHenry county). Those readings at thermometer level were chilly enough to support patchy frost at ground level.
The COOL AIR is occurring with a huge pool of cool air draped across eastern Canada, the Midwest and the Northeast U.S.—a cold pool aloft which is hemmed in by the latest atmospheric blocking pattern.
The cool temps represent a sea change from the 80s earlier in October. That warmth has the opening 9 days of October this year running more than 7-deg warmer than a comparable pattern a year ago.
The Chicago area is headed for what looks to be AN EXTENDED PERIOD OF WET, WINDY WEATHER this week—-rain which are likely to commence late Wednesday and Wed night—then run into Sunday.
The stormy autumn pattern expected to produce those rains may even become thundery at times Friday and Friday night, a period likely to coincide with the heaviest rainfall. IT’S AT THAT TIME THE MAXIMUM FLOW OF MOIST GULF AIR INTO THE AREA WILL BE OCCURRING—though rains before and after the period may contribute to what could amount to 1.50 to local 3+” total rains.
Modeling brings the storm expected to generate the rainy, windy weather out of Colorado—tracking it across central Illinois and Indiana, thus keeping a easterly flow blowing into Chicago off the 60-deg lake waters—waters which have cooled nearly 13-degrees since their peak back in August.
While temps last week averaged 9-deg above normal, by the time the book closes on the coming week’s temps, reading are projected to come in 4-deg below normal and average 1-2 deg below normal next week.
HERE’S MY LATEST MONDAY CHICAGO METRO FORECAST (10/9/2023)
FROST ADVISORY 1am to 8am CDT TONIGHT INTO TUESDAY MORNING in all but COOK AND LAKE COUNTIES in northeast Illinois
TONIGHT: Scattered clouds and chilly. Temps nearly 10-degrees below the normal low of 48-deg. Lows 39 at O’Hare—but closer to freezing in the coldest inland locations while low 40s occur along Lake Michigan.
TUESDAY: Sunshine through mixed fair weather clouds, cool for the season. High 61.
TUESDAY NIGHT: Scattered clouds, continued chilly. Low 40—but with low and mid 30s and areas of frost possible again inland.
WEDNESDAY: Increasing cloudiness, temps similar to those of recent days. Chance of a few showers southern sections late. High 61.
WEDNESDAY NIGHT AND THURSDAY: Cloudy and turning breezy. Some rain at times. Low Wed night 46. High Thursday 57.
FRIDAY: Rainy and windy. Locally heavy rainfall with some thundery spells not out of the question. High 60.
SATURDAY: Occasional rain, cool, damp and breezy. High 56.
SUNDAY: Cloudy, breezy and cool. Some showery spells or passing sprinkles. High 55.
MONDAY: Cloudy and windy—possible showers, especially in areas adjacent to Lake Michigan. High 54.