Hazard Report Provided By forecast.weather.gov

Hazardous Weather Outlook
National Weather Service Chicago/Romeoville IL
420 AM CDT Wed Aug 12 2026

ILZ003>006-008-010>013-019>021-023-032-033-039-103>108-INZ001-002-
010-011-019-130930-
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-
420 AM CDT Wed Aug 12 2026 /520 AM EDT Wed Aug 12 2026/

This Hazardous Weather Outlook is for portions of north central
Illinois...northeast Illinois and northwest Indiana.

.DAY ONE...Today and Tonight.

Weather hazards expected...

  Elevated Thunderstorm Risk...with an associated:
     Level 1 of 5 Tornado Risk.
     Level 2 of 5 Damaging Wind Risk...up to 75 mph.
     Level 1 of 5 Large Hail Risk...up to quarter size.
  Elevated Flooding Risk.

DISCUSSION...

Isolated thunderstorms are possible early this morning, the
strongest of which may be capable of producing brief hail and
localized downpours.

A fast-moving line of strong to severe thunderstorms is then
expected to move east across the area from mid-morning into early
this afternoon. These storms will have the potential to produce
damaging winds and isolated tornadoes, in addition to producing
torrential rains which may lead to localized flooding. At this
time, the greatest risk of severe would appear to be from the I-88
corridor south and eastward.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Thursday and Friday...
  Elevated Flooding Risk.
  Limited Thunderstorm Risk...with an associated:
     Level 1 of 5 Severe Thunderstorm Risk.
Saturday...
  Elevated Flooding Risk.
  Limited Thunderstorm Risk.
Sunday...
  Limited Thunderstorm Risk.

DISCUSSION...

An active weather pattern with periodic thunderstorm chances is
expected to persist into the weekend. Some of these storms may be
strong to severe at times, as well as capable of producing heavy
rainfall which could lead to flash flooding.

.SPOTTER INFORMATION STATEMENT...

  Spotters may be needed from mid-morning into early this
  afternoon.

GENERAL STORM MOTION OF THE DAY:

  Moving toward the east-southeast at around 35 mph for early morning
  storms. If mid-morning storms form a bowing line, it may move east at
  45 to 55 mph.


$$

Flood Warning
National Weather Service Chicago IL
848 PM CDT Tue Aug 11 2026

...The National Weather Service in Chicago has issued a Flood Warning
for the following rivers in Illinois...

  Thorn Creek at Thornton affecting Cook County.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Flood Warning means water levels above flood stage are imminent or
may already be occurring. Persons along rivers and streams in the
warned area should take immediate precautions to protect life and
property.

These forecasts are based on observed precipitation as well as
forecast precipitation 24 hours into the future. Changes to the
rainfall forecast, or any additional rainfall after 24 hours, may
cause changes to these river forecasts.

Additional information is available at www.weather.gov.

The next statement will be issued by Wednesday afternoon.

&&

ILC031-122000-
/O.NEW.KLOT.FL.W.0068.260812T0148Z-260813T2100Z/
/THNI2.1.ER.260811T2331Z.260812T0600Z.260813T1500Z.NO/
848 PM CDT Tue Aug 11 2026

...FLOOD WARNING IN EFFECT FROM THIS EVENING TO THURSDAY AFTERNOON...

* WHAT...Minor flooding is occurring and minor flooding is forecast.

* WHERE...Thorn Creek from Near Glenwood downstream to confluence
  with Little Calumet River, including the Thornton gauge.

* WHEN...From this evening to Thursday afternoon.

* IMPACTS...At 11.0 feet, 187th Street threatened in Glenwood.

* ADDITIONAL DETAILS...
  - At 8:30 PM CDT Tuesday the stage was 9.6 feet.
  - Forecast...The river is expected to rise to a crest of 10.7 feet
    just after midnight tonight. It will then fall below flood stage
    late Thursday morning.
  - Flood stage is 9.0 feet.
  - http://www.weather.gov/safety/flood

&&

LAT...LON 4161 8760 4158 8754 4151 8760 4154 8767


$$

Petr

Hazard Report Provided By forecast.weather.gov