MONDAY’S LOW 60s MORE TYPICAL OF MID-OCTOBER THAN EARLY/MID SEPT–MONDAY RECORDS CHICAGO’S COOLEST TEMP SINCE MAY (IN 4 MONTHS)–BUT THE BIG WEATHER STORY THIS WEEK INTO NEXT: WARMING-TEMPS BY THURSDAY AND COULD BE FLIRTING WITH 90 THIS TIME NEXT WEEK.

We’re in the midst of an early autumn preview–one WHICH WILL NOT LAST.

Strong warming is to follow, and we could be flirting with 90-deg a week from now in what looks likely to be a period of UNSEASONABLE WARMTH. You can already see warming and southerly winds returning to the Plains.

But it certainly wasn’t warm today. This was a jacket and sweater day here–the first in months. Low 60-degree highs, like those we saw in the wake of Chicago’s weekend deluge, was more typical of late April or and mid-October. Put a bit differently, the level of cool, early season air we have experienced on Monday typically occurs a month from now.

We’ve not had a daytime high as cool as today’s low 60s in more than 5 months–since a 53-deg high back on May 5th. My check of weather records shows Sept 12th has only produced AS COOL OR COOLER THAN TODAY’s SEVEN TIMES in the past 150 years.

But modeling continues to show major warming lies ahead. 80s return to Chicago (except for a lake breeze) on Thursday—and the early read on early next week suggests UNSEASONABLY WARM WEATHER is to lock in late this coming week into the first half of next week. Daytime temps will average 9 to 15-deg ABOVE NORMAL from Friday through next Wednesday.