It’s DRY HERE as we head into September, 2023, and we have NO RAIN currently anticipated into mid-next week

• It hasn’t rained a drop officially in Chicago at O’Hare in 15 days (since 0.20” fell back on August 17).
• Frank Wachowski notes we finished August in NEAR RECORD TERRITORY
• Much of the Chicago area is in an “abnormally dry” state with western counties in a state of MODERATE DROUGHT according to the latest DROUGHT MONITOR WHICH CAME OUT YESTERDAY. It’s going to be interesting to see how our drought status changes with next week’s DROUGHT MONITOR release.
• August finished with LESS THAN ONE-THIRD OUR NORMAL RAINFALL–just 1.33” versus the “normal” for August of 4.25.”
• Check out how widespread the dry weather was across the Corn Belt and central and northern Midwest.
• August ranked 25th driest of the past 153 Augusts dating back to 1871. That places the month among the driest 16% of all Augusts on the books here–particularly striking, because August has historically been Chicago’s second driest month of the year.

THE BEGINNING OF THE UNSEASONABLE LATE SEASON HOT DOME BUILDING OVER WIDE SWATH OF THE NATION FOR THE LABOR DAY HOLIDAY WEEKEND AS IT LOOKS ON FRIDAY UPPER AIR ANALYSES

It means 90s are on their way to Chicago–heat that initially comes in without oppressive humidities but a hot spell which is to grow decidedly MORE HUMID next week.

LAKE MICHIGAN’S WARMTH boosted shoreline Friday morning low temps by more than 20-degrees over their INLAND COUNTERPARTS

We’re moving into “WARMER NEAR THE LAKE AT NIGHT” season!

• Low temps Friday morning warmed across the area compared to the morning before. O’Hare’s overnight low was 58 degrees Friday compared to 53 degrees the morning before. And Midway’s low temp Friday morning was up 6 degrees from the morning before.
• And they’re going to see nighttime min temps warm additionally as a Labor Day weekend HOT AIR DOME builds over the area.
• So often, we think of Lake Michigan’s impact on local weather as having a COOLING EFFECT. And, it OFTEN does have a cooling effect by day in the warm season. But, as we move into cooler periods of the year–OVERNIGHT FOR INSTANCE–the impact of Lake Michigan on the shoreline climate often reverses at night. You might say we’re heading into the “WARMER NEAR THE LAKE AT NIGHT” SEASON. That’s because lake weather temps change far more slowly than the air surrounding the Great Lakes. Lake water RETAINS summer heat going into fall and winter. So at night, as inland temps CRASH, warm lake waters restrain cooling along and out over the lake.

FOR OUR LABOR DAY WEEKEND MARINERS

• A strengthening pressure gradient means well organized “offshore” southwest winds—in other words, winds which blow FROM the southwest and out over Lake Michigan–will override and cool. And since the winds are blowing offshore, the waves they generate will grow in height the farther offshore one goes.
• HERE ARE A SERIES OF LAKE MICHIGAN WAVE HEIGHT FORECASTS through the Labor Day weekend showing the how winds and waves pick up each day with daytime heating—then ease a bit during the night and early morning.
• The tallest waves will occur east and north of Chicago where the “SW” winds will have been able to spend more time over waters thus building taller waves.