FIRST, THE MONDAY WEATHER HEADLINES

–By the time the books close on this 3rd day of October, Chicago will have recorded its 12th consecutive day of below normal temps in Chicago.

–October’s off to a cool opening 3 days compared to Oct 1-3 a year ago. Temps for the period this year are running 14.4-deg cooler than the opening 3-days of the month a year ago.

–The high today was 68—compared to 76 on this date a year ago. But get this. It was 91 deg on this date 68 years ago (in 1954) at both O’Hare and Midway

–Last week (Monday through Saturday) averaged nearly 6-deg below normal; this week is to average 4-degree below normal but will come in 1.2-deg cooler overall than last week.

–Having said that, a nice mild spell is on the way Tuesday and Wednesday with the first back-to-back 70-deg or warmer highs here in two weeks (since mid 80s Sept 20-21). Thursday won’t be far from 70-deg either.

–BUT a strong cold front passes and ushers a 1036 mb Canadian high pressure into the area late Thursday into the coming weekend. This is to deliver the first 30s to the city of the season on Friday and Saturday nights with daytime highs likely to hold to the 50s for the first time this fall. It’s a cool spell likely to produce the Chicago area’s first back-to-back daytime highs limited to the 50s in the nearly 5 months since early May of this past spring.  The front is NOT likely to produce huge amounts of precip continuing a drier than normal weather regime which has dominated since 0.44″ of rain fell more than 3 weeks ago on Sept 18. You have to go back to Sept 11th to find our last 1″ or greater official rainfall here in Chicago.

–Average daytime temps between this coming Friday and next Monday will average 6 to 13-deg below normal each day.

–Temps for the Chicago Marathon Sunday morning look cool, which should be to the liking of runners this year. Early indications suggest low and mid 40s at race time with WNW winds 6 to 15 mph.

–Warming follows early next week–but modeling suggests another cool spell hits later next week. A “Greenland block” is to develop–often a COOL SIGNAL for Chicago.

HERE’S THE LATEST CHICAGO METRO FORECAST

TONIGHT: Mainly clear and cool. Low 45 in the city–close to 40 coolest inland locations.

TUESDAY: Generous sunshine, a bit milder in the afternoon. The first 70-deg high in 10 days. High 73.  Light winds turn off Lake Michigan late morning and afternoon.

TUESDAY NIGHT: Clouding over. Not quite as cool. Low 49.

WEDNESDAY: A good deal of cloudiness but with some mixed sun, seasonably mild. Chance of a few spotty light showers late. High 74.

THURSDAY: Cloudy spells, turning breezy and cooler in the afternoon and evening–a noticeably cooler at night. A few light scattered showers possible impacting 30 to 40% of the area. High 69–but falling off in the afternoon.

FRIDAY: Windy and much cooler. Clouds and some mixed sun. A few lake effect sprinkles or showers near the southeast of Lake Michigan, including the northwest Indiana and possibly the northeast Illinois shoreline.  High 55.

SATURDAY: Mostly sunny but cool and a bit breezy.  High 55.

SUNDAY: Cool with sunny skies giving way to increasing cloudiness in the afternoon. High 62.

MONDAY: More clouds than not, breezy and milder. Growing prospects for showers. High 67.