Hazard Report Provided By forecast.weather.gov

Hazardous Weather Outlook
National Weather Service Chicago/Romeoville IL
403 AM CDT Thu Aug 13 2026

ILZ003>006-008-010>013-019>021-023-032-033-039-103>108-INZ001-002-
010-011-019-140915-
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-
403 AM CDT Thu Aug 13 2026 /503 AM EDT Thu Aug 13 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 60 mph.
     Level 1 of 5 Large Hail Risk...up to quarter size.
  Elevated Flooding Risk tonight.
  Significant Fog Risk this morning.

DISCUSSION...

Areas of dense fog are expected early this morning mainly west
and south of Chicago.

There is a chance of thunderstorms this afternoon, and some of
these storms could be severe with primarily a damaging wind threat
mainly south of a Mendota to Rensselaer line.

Showers and thunderstorms are expected across the area tonight,
and are likely to pose a threat of locally heavy rainfall that may
lead to flooding . At this time, the heaviest rainfall is
expected to occur generally south of a Forreston Illinois to
Valparaiso Indiana line.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

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

DISCUSSION...

An active weather pattern is expected to persist into this
weekend, with periodic shower and thunderstorm chances. These
showers and storms will be capable of producing torrential
rainfall at times, which could lead to flooding or flash
flooding.

.SPOTTER INFORMATION STATEMENT...

  Spotters may be needed this afternoon within a region
   mainly south of a Mendota to Rensselaer late.

GENERAL STORM MOTION OF THE DAY:

  Moving toward the southeast at 25 to 35 mph.

$$

URGENT - WEATHER MESSAGE
National Weather Service Chicago IL
242 AM CDT Thu Aug 13 2026

ILZ003-004-008-010>013-019>021-023-032-033-039-105>108-INZ001-002-
010-011-019-131400-
/O.NEW.KLOT.FG.Y.0013.260813T0742Z-260813T1400Z/
Winnebago-Boone-Ogle-Lee-De Kalb-Kane-DuPage-La Salle-Kendall-
Grundy-Kankakee-Livingston-Iroquois-Ford-Southern Cook-Northern
Will-Southern Will-Eastern Will-Lake IN-Porter-Newton-Jasper-
Benton-
Including the cities of Rochelle, Mokena, Portage, Channahon,
Watseka, Hammond, Orland Park, Crete, Pontiac, Dwight, Byron,
Morocco, Oswego, Oxford, Fairbury, Gary, Aurora, Lemont, Valparaiso,
Downers Grove, Streator, Beecher, Chesterton, Yorkville, Fowler,
Peotone, La Salle, Bradley, Minooka, Elgin, Manhattan, Wheaton,
Lombard, Marseilles, Sycamore, Bourbonnais, Rockford, Dixon, Mendota,
Kankakee, Park Forest, Bolingbrook, Plainfield, Rensselaer,
Naperville, DeMotte, Ottawa, Calumet City, Carol Stream, Gilman,
Belvidere, Oak Forest, Joliet, Merrillville, Kentland, Oregon, Gibson
City, DeKalb, Morris, Plano, Wilmington, Roselawn, Coal City, and
Paxton
242 AM CDT Thu Aug 13 2026 /342 AM EDT Thu Aug 13 2026/

...DENSE FOG ADVISORY IN EFFECT UNTIL 9 AM CDT /10 AM EDT/ THIS
MORNING...

* WHAT...Visibility one quarter mile or less in dense fog.

* WHERE...Portions of central, east central, north central, and
  northeast Illinois and northwest Indiana.

* WHEN...Until 9 AM CDT /10 AM EDT/ this morning.

* IMPACTS...Low visibility could make driving conditions hazardous.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If driving, slow down, use your headlights, and leave plenty of
distance ahead of you.

&&

$$

Ratzer

Flood Statement
National Weather Service Chicago IL
953 PM CDT Wed Aug 12 2026

...The Flood Warning continues for the following rivers in
Illinois...

  Thorn Creek at Thornton affecting Cook County.

For the Thorn Creek...including Thornton...Minor flooding is
forecast.

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 Thursday afternoon.

&&

ILC031-132000-
/O.EXT.KLOT.FL.W.0068.000000T0000Z-260813T2000Z/
/THNI2.1.ER.260811T2331Z.260812T0830Z.260813T1400Z.NO/
953 PM CDT Wed Aug 12 2026

...FLOOD WARNING NOW IN EFFECT UNTIL 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...Until Thursday afternoon.

* IMPACTS...At 9.0 feet, Water begins to be diverted through Thorn
  Creek Diversion Tunnel.

* ADDITIONAL DETAILS...
  - At 9:30 PM CDT Wednesday the stage was 9.4 feet.
  - Recent Activity...The maximum river stage in the 24 hours ending
    at 9:30 PM CDT Wednesday was 10.6 feet.
  - Forecast...The river has crested and is expected to gradually
    fall overnight. It will fall below flood stage late tomorrow
    morning.
  - Flood stage is 9.0 feet.
  - http://www.weather.gov/safety/flood

&&

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


$$

Yack

Hazard Report Provided By forecast.weather.gov