Scattered thunderstorms moved across southern Lake Michigan during the afternoon and evening of August 24th.
Every event with a place to put it. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS LOT wrote it up.
Scattered thunderstorms moved across southern Lake Michigan during the afternoon and evening of August 24th.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Chicago, IL wrote its last area forecast discussion before the first event at Aug 24, 2:17 PM CST, 38 minutes earlier.
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>Service Notice</title>
<link rel="stylesheet" href="index.css">
</head>
<body>
<main class="wrap">
<section class="card" role="status" aria-live="polite">
<div class="status" id="status">Temporary Notice</div>
<h1 id="headline">This service is currently unavailable.</h1>
<p id="message1">
The site you requested is temporarily down for maintenance or an unexpected outage.
</p>
<p id="message2">
Please try again in a few minutes.
</p>
<p class="small" id="detail">
If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
</p>
</section>
</main>
<script src="index.js"></script>
</body>
</html>Hazardous Weather Outlook
National Weather Service Chicago/Romeoville IL
1236 PM CDT Tue Aug 24 2021
ILZ003>006-008-010>013-019>021-023-032-033-039-103>108-INZ001-002-
010-011-019-251745-
Winnebago-Boone-McHenry-Lake IL-Ogle-Lee-De Kalb-Kane-DuPage-
La Salle-Kendall-Grundy-Kankakee-Livingston-Iroquois-Ford-
Northern Cook-Central Cook-Southern Cook-Northern Will-
Southern Will-Eastern Will-Lake IN-Porter-Newton-Jasper-Benton-
1236 PM CDT Tue Aug 24 2021 /136 PM EDT Tue Aug 24 2021/
This Hazardous Weather Outlook is for portions of North Central
Illinois...Northeast Illinois and Northwest Indiana.
.DAY ONE...This Afternoon and Tonight.
Weather hazards expected...
Limited Thunderstorm Risk...with an associated:
Limited damaging wind risk...up to 60 mph.
Limited hail risk...up to quarter size.
Limited Flooding Risk.
Elevated Excessive Heat Risk.
DISCUSSION...
Thunderstorms stretching from northern Iowa to central Wisconsin
as of mid day may move into areas mainly north of I-88 toward and
after sunset this evening. The main threat would be wind gusts
strong enough to down tree limbs if these storms do affect the
area and remain strong to severe. Additional thunderstorms are
possible in the late evening and overnight. Any thunderstorm
through tonight will produce torrential downpours capable of
producing ponding on roadways and possibly localized flooding.
Hot and humid conditions with heat index values of 100 to 110
degrees will continue through the afternoon.
.DAYS TWO THROUGH SEVEN...Wednesday through Monday.
Wednesday...
Limited Thunderstorm Risk.
Elevated Excessive Heat Risk.
Thursday through Sunday...
Limited Thunderstorm Risk.
Limited Excessive Heat Risk.
Monday...
Limited Thunderstorm Risk.
DISCUSSION:
Hot and humid conditions are expected through at least Wednesday
with heat indices over 100 possible. Periodic thunderstorms will
occur as well, though many hours will stay dry.
.SPOTTER INFORMATION STATEMENT...
Spotters may be needed in the evening, mainly north of I-80.
GENERAL STORM MOTION OF THE DAY:
Moving toward east and east-southeast at 30 to 35 mph.
LMZ740>745-251745-
Winthrop Harbor to Wilmette Harbor IL-
Wilmette Harbor to Northerly Island IL-
Northerly Island to Calumet Harbor IL-
Calumet Harbor IL to Gary IN-Gary to Burns Harbor IN-
Burns Harbor to Michigan City IN-
1236 PM CDT Tue Aug 24 2021
This Hazardous Weather Outlook is for portions of the Illinois
nearshore waters of Lake Michigan and the Indiana nearshore
waters of Lake Michigan.
.DAY ONE...This Afternoon and Tonight.
Weather hazards expected...
Limited Thunderstorm Risk...with an associated:
Limited thunderstorm wind gust risk...up to 40 to 50 knots.
Limited hail risk...up to nickel to quarter size.
.DAYS TWO THROUGH SEVEN...Wednesday through Monday.
Wednesday through Monday...
Limited Thunderstorm Risk.
Castro
Visit us at http://weather.gov/chicago
Follow us on Facebook, Twitter, and Youtube at:
www.facebook.com/nwschicago
www.twitter.com/nwschicago
www.youtube.com/nwschicagoThe Chicago radar (KLOT), 87 km away, was scanning. The volume nearest the first event began at 20:56 UTC.
9 marine thunderstorm wind. Local standard time, as filed.
A group of 18 sailing boats were offshore of Evanston when a strong thunderstorm outflow boundary moved through capsizing 8 of the boats. At least 23 people were in the water and at least 8 were rescued by first responders but no injuries were reported. Many of the capsized boats washed up along the Lake Michigan shore near Evanston.
Winds gusted above 34 knots for 22 minutes with a peak gust to 39 knots.
Winds gusted above 34 knots for 44 minutes with a peak gust to 70 knots as the storms arrived.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Lake Michigan in 2021Every state in 2021This day in weather history
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-10-01. Each event’s entry at NCEI: 978685, 978697, 978688, 978689, 978691, 978683, 978682, 978692, 978693.