National Weather Service United States Department of Commerce

Chicago, IL

Weather Forecast Office

August 18th, 2025: Severe Weather and Flash Flooding

Weather.gov > Chicago, IL > August 18th, 2025: Severe Weather and Flash Flooding

 

Event Summary Graphic

 

Overview

  • A warm, humid, and unstable airmass set the table for shower and storm development and multiple rounds of storms through the afternoon and into the evening on August 18th.
  • The first round of storms were confined the Wisconsin state line with special weather statements being issued for Winnebago, Boone, and McHenry counties. No damage was reported, but isolated personal weather stations recorded wind gusts up to 40 mph. 
  • The afternoon sun eroded away a lingering cap, which allowed storms to tap into building instability.  Small supercells started to develop along a weak outflow boundary across northwest Illinois. Those cells would eventually merge and form a quasi-linear convective system (QLCS). Damage that was reported in DeKalb County was consistent with straight line winds.
  • This line of storms had a tremendous amount of water vapor available and storms produced very heavy rainfall. Radar estimated hourly rain rates at times approached 2 to 4 inches. These high rates resulted in numerous instances of flash flooding due to how quickly it was falling onto an already saturated soil (or a concrete urban environment). 
  • The line of storms would slow and form a nearly east-west boundary between the I-88 and I-80 corridors, prompting the issuance of several flash flood warnings. Localized rain totals were up to 8 inches were estimated by radar in parts of Lee, DeKalb, and Lake (IN).

August 18th Severe Weather

Preliminary Map of Storm Reports

Preliminary Storm Report Map

Preliminary National Storm Reports

Interactive Map of Preliminary Storm Reports

 
Preliminary Local Storm Report...Summary
National Weather Service Chicago IL
127 PM CDT Tue Aug 19 2025

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0818 PM     Tstm Wnd Gst     3 NNW Plainfield        41.65N 88.22W
08/18/2025  M58 MPH          Will               IL   Trained Spotter  

             

0348 PM     Tstm Wnd Dmg     Genoa                   42.10N 88.69W
08/18/2025                   De Kalb            IL   Emergency Mngr   

            Tree damage around Genoa, north and south of 
            town. Time estimated from radar. 

0350 PM     Tstm Wnd Dmg     2 NE Genoa              42.12N 88.67W
08/18/2025                   De Kalb            IL   Emergency Mngr   

            Many trees down northeast of Genoa along Ash 
            Road between North State and Illinois Route 
            23. Damage includes poles, trees and wires. 
            Time estimated from radar. 

0352 PM     Tstm Wnd Dmg     2 E Genoa               42.10N 88.65W
08/18/2025                   De Kalb            IL   Emergency Mngr   

            Large tree across the whole road, Illinois 
            23 north of Illinois 72, northeast of Genoa. 
            Time estimated from radar. 

0406 PM     Tstm Wnd Dmg     4 WNW Sycamore          42.01N 88.75W
08/18/2025                   De Kalb            IL   Emergency Mngr   

            Three power poles down on Old State Road 
            between Five Points Road and Church Rd west 
            of Sycamore. Time estimated from radar. 


&&

$$

August 18th Heavy Rain and Flash Flooding

Preliminary National Flash Flooding Reports

 

Flash Flood Reports: 

Preliminary Local Storm Report...Summary
National Weather Service Chicago IL
359 PM CDT Tue Aug 19 2025

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0835 PM     Flash Flood      1 WSW Gary Airport      41.61N 87.44W
08/18/2025                   Lake               IN   Public           

            Multiple public reports on social media of 
            basement flooding in East Chicago. Video 
            shows nearby street and yard flooding. 

0835 PM     Flash Flood      2 SSE Whiting           41.66N 87.48W
08/18/2025                   Lake               IN   Public           

            US 20 closed due to flooding. Relayed via 
            social media. 

0841 PM     Flash Flood      1 SSE Whiting           41.66N 87.48W
08/18/2025                   Lake               IN   Emergency Mngr   

            Indianapolis Blvd at 128th has about 3 feet 
            of water and is being closed to traffic. 

0930 PM     Flash Flood      Whiting                 41.69N 87.50W
08/18/2025                   Lake               IN   Local Official   

            Combined sewer storage facility exceeded 
            capacity and overflowed due to heavy 
            rainfall. Relayed via broadcast media. Time 
            estimated based upon nearby reports. 

0930 PM     Flash Flood      1 WSW Whiting           41.68N 87.51W
08/18/2025                   Lake               IN   Local Official   

            Multiple basements flooded in Hammond. Time 
            estimated based upon nearby reports. Relayed 
            via broadcast media. 

0945 PM     Flash Flood      2 SSE Gary Airport      41.59N 87.40W
08/18/2025                   Lake               IN   Public           

            Public reports of basement flooding in Gary. 
            Time estimated based upon nearby reports. 

0946 PM     Flash Flood      2 E Hammond             41.59N 87.46W
08/18/2025                   Lake               IN   Public           

            Public report of basement flooding in 
            Hessville neighborhood of Hammond near 
            Morton Elementary. 

1000 PM     Flash Flood      Whiting                 41.68N 87.50W
08/18/2025                   Lake               IN   Public           

            Up to 3 feet of water on Indianapolis 
            Boulevard from 120th to 129th and the areas 
            of Dickey and Riley roads. 

0633 PM     Flash Flood      2 NE Roscoe             42.44N 88.99W
08/18/2025                   Winnebago          IL   Public           

            Report relayed from mPING of street 
            flooding. 

0725 PM     Flash Flood      2 E Rockton             42.46N 89.04W
08/18/2025                   Winnebago          IL   Public           

            Public report of street flooding near 
            Rockton Road and Dorr Road. Flooding 
            extending into nearby yards. 

0652 PM     Flash Flood      Lockport                41.59N 88.05W
08/18/2025                   Will               IL   Public           

            Report relayed from mPING of street 
            flooding. 

0716 PM     Flash Flood      1 SE Lockport           41.58N 88.05W
08/18/2025                   Will               IL   Public           

            Report relayed from mPING of street 
            flooding. 

0735 PM     Flash Flood      2 SE Lockport           41.57N 88.03W
08/18/2025                   Will               IL   Public           

            Report relayed from mPING of street 
            flooding. 

0738 PM     Flash Flood      2 E Mokena              41.54N 87.84W
08/18/2025                   Will               IL   Public           

            Report relayed from mPING of street 
            flooding. 

0755 PM     Flash Flood      2 NE Mokena             41.55N 87.85W
08/18/2025                   Will               IL   Public           

            At least 6 inches of water in underpass 
            under railroad tracks. 

0900 PM     Flash Flood      3 NW Bolingbrook        41.73N 88.12W
08/18/2025                   Will               IL   NWS Employee     

            1 to 1.5 feet of standing water at the 
            intersection of Naper Blvd and 87th Street. 
            Around 1 foot of water on roads encroaching 
            on driveways in surrounding neighborhoods, 
            and at least 6 inches of flowing water at 
            Arlington and Riverwoods. 

0910 PM     Flash Flood      Joliet                  41.53N 88.08W
08/18/2025                   Will               IL   Public           

            Reports of standing or flowing water on many 
            streets or intersections of Joliet. 

1000 PM     Flash Flood      2 ENE Mokena            41.54N 87.84W
08/18/2025                   Will               IL   Public           

            Up to 3 feet of water on roadway. 

1241 AM     Flash Flood      2 E Mokena              41.54N 87.84W
08/19/2025                   Will               IL   Public           

            Several reports from mPing of flooded and 
            closed roads in Mokena. 

0600 PM     Flash Flood      Compton                 41.69N 89.09W
08/18/2025                   Lee                IL   Public           

            Video shared to social media shows several 
            inches of flowing water on roadways and a 
            parking lot in Compton. 

0730 PM     Flash Flood      1 N Paw Paw             41.71N 88.98W
08/18/2025                   Lee                IL   Public           

            Report on social media of Paw Paw Road 
            flooded approximately half mile north of Paw 
            Paw. Possibly near creek crossing at Dredge 
            Road. 

0730 PM     Flash Flood      1 NW La Salle           41.34N 89.10W
08/18/2025                   La Salle           IL   Public           

            Report relayed from mPING of street 
            flooding. 

0800 PM     Flash Flood      2 SE Yorkville          41.62N 88.43W
08/18/2025                   Kendall            IL   Public           

            Street flooded with at least 6 inches of 
            standing water. 

0809 PM     Flash Flood      1 S Oswego              41.67N 88.36W
08/18/2025                   Kendall            IL   Public           

            Report relayed from mPING of street 
            flooding. 

0535 PM     Flash Flood      2 NNE Woodridge         41.78N 88.04W
08/18/2025                   DuPage             IL   NWS Employee     

            In Downers Grove, 6-8 inches of water 
            flowing over the road at Belmont near 59th 
            Street. 

0610 PM     Flash Flood      1 W Downers Grove       41.79N 88.02W
08/18/2025                   DuPage             IL   Public           

            Report relayed from mPING of street 
            flooding. 

0625 PM     Flash Flood      1 NW Darien             41.76N 87.98W
08/18/2025                   DuPage             IL   Public           

            Report on social media with photos showing 
            4-6 inches of water on Washington Street in 
            Darien, with flooding also impacting houses. 

0836 PM     Flash Flood      1 E Downers Grove       41.79N 88.00W
08/18/2025                   DuPage             IL   Public           

            Report relayed from mPING of street 
            flooding. 

0837 PM     Flash Flood      3 NW Bolingbrook        41.73N 88.10W
08/18/2025                   DuPage             IL   Public           

            Report relayed from mPING of street 
            flooding. 

0910 PM     Flash Flood      1 SSE Naperville        41.76N 88.14W
08/18/2025                   DuPage             IL   Public           

            1 to 2 feet of water reported on Gartner 
            Road with vehicles stranded. Unclear exactly 
            where on Garner Road this is occurring. 

0640 PM     Flash Flood      3 E Paw Paw             41.69N 88.93W
08/18/2025                   De Kalb            IL   Public           

            Video posted to social media shows at least 
            a foot of flowing water over Chicago Road 
            east of Paw Paw. 

0741 PM     Flash Flood      2 S Orland Hills        41.57N 87.84W
08/18/2025                   Cook               IL   Public           

            Report relayed from mPING of street 
            flooding. 

0807 PM     Flash Flood      1 SE Orland Hills       41.57N 87.83W
08/18/2025                   Cook               IL   Public           

            Report relayed from mPING of street 
            flooding. 

0809 PM     Flash Flood      2 W Orland Hills        41.59N 87.88W
08/18/2025                   Cook               IL   Public           

            Report relayed from mPING of street 
            flooding. 

0815 PM     Flash Flood      1 NE Tinley Park        41.59N 87.78W
08/18/2025                   Cook               IL   Public           

            A few public reports of basement flooding in 
            Tinley Park. Relayed via social media. 
            Photos and videos show flooded roadways with 
            at least several inches of flowing water in 
            the vicinity. Time estimated based upon 
            nearby reports. 

0834 PM     Flash Flood      1 W Midlothian          41.63N 87.73W
08/18/2025                   Cook               IL   Public           

            Report relayed from mPING of street 
            flooding. 

1000 PM     Flash Flood      Thornton                41.58N 87.62W
08/18/2025                   Cook               IL   Public           

            2 lanes covered in water near the quarry on 
            I294. 

1244 AM     Flash Flood      2 S Orland Hills        41.57N 87.84W
08/19/2025                   Cook               IL   Public           

            Several reports from from mPING of flooded 
            streets. 

0600 AM     Flash Flood      3 WNW Orland Park       41.63N 87.90W
08/19/2025                   Cook               IL   Law Enforcement  

            143rd Street closed due to flooding near 
            Creek Crossing Drive. Relayed via social 
            media. 

0600 AM     Flash Flood      3 WSW Orland Hills      41.58N 87.89W
08/19/2025                   Cook               IL   Law Enforcement  

            Wolf Road flooded near 167th Street near 
            Marley Creek crossing. Relayed via social 
            media. 


&&

 

August 16 Through the 19th: 3-day Rainfall Totals

Preliminary National Flash Flooding Reports

Selected Rainfall Reports: 

Public Information Statement
National Weather Service Chicago IL
1127 AM CDT Tue Aug 19 2025

...PRECIPITATION TOTALS SINCE AUGUST 16, 2025...

Location                     Amount    Time/Date       Provider             

...Illinois...

...Cook County...
Oak Forest 1 NNW             6.60 in   0700 AM 08/19   COCORAHS             
Lansing 2 S                  5.72 in   0700 AM 08/19   COOP                 
Matteson 0.9 E               5.72 in   0700 AM 08/19   COCORAHS             
Crestwood 0.4 SW             5.70 in   0720 AM 08/19   COCORAHS             
Flossmoor 1 SE               5.35 in   0700 AM 08/19   COCORAHS             
Midlothian                   5.26 in   0700 AM 08/19   COCORAHS             
Elk Grove Village 2 WSW      5.05 in   0805 AM 08/19   COCORAHS             
Midlothian 1 SSE             5.04 in   0800 AM 08/19   COCORAHS             
Elk Grove Village 1 ESE      4.99 in   0700 AM 08/19   COCORAHS             
Homewood                     4.76 in   0700 AM 08/19   COCORAHS             
Park Forest 1 WNW            4.73 in   0730 AM 08/19   COCORAHS             
Lansing Airport              4.69 in   0955 AM 08/19   AWOS                 
Palos Park 2 WSW             4.63 in   0700 AM 08/19   COCORAHS             
Park Forest 1 NNE            4.58 in   0700 AM 08/19   COCORAHS             
Hoffman Estates              4.42 in   0700 AM 08/19   COCORAHS             
Arlington Heights 1 W        4.42 in   0700 AM 08/19   COCORAHS             
Barrington 3 SW              4.26 in   0800 AM 08/19   COOP                 
Chicago OHare                4.17 in   0951 AM 08/19   ASOS                 
Schaumburg 2 E               4.14 in   0700 AM 08/19   COCORAHS             
Merrionette Park - 1 WSW     4.10 in   0700 AM 08/19   COCORAHS             
La Grange Park 1 SSW         4.09 in   0700 AM 08/19   COCORAHS             
Hoffman Estates 2.5 NNE      4.01 in   0756 AM 08/19   COCORAHS             
South Holland - Little Calum 4.01 in   0945 AM 08/19   MESONET                 
Park Forest                  4.00 in   0500 AM 08/19   COOP                 

...DuPage County...
Downers Grove 1.8 SSE        5.33 in   0700 AM 08/19   COCORAHS             
Aurora 4 ESE                 5.08 in   0700 AM 08/19   COCORAHS             
Naperville 3 SE              5.06 in   0700 AM 08/19   COCORAHS             
Clarendon Hills              5.05 in   0700 AM 08/19   HYDRO                
Westmont 1.1 SSW             5.02 in   0700 AM 08/19   COCORAHS             
Bartlett 1.1 SE              4.88 in   0700 AM 08/19   COCORAHS             
Naperville 3 SE              4.87 in   0700 AM 08/19   COCORAHS             
Aurora 4 ESE                 4.87 in   0700 AM 08/19   COCORAHS             
Aurora 4 ESE                 4.87 in   0800 AM 08/19   COCORAHS             
Carol Stream                 4.80 in   0700 AM 08/19   COCORAHS             
Morton Arboretum             4.43 in   0700 AM 08/19   COOP                 
Warrenville - W. Br. DuPage  4.04 in   0925 AM 08/19   MESONET                 
Bolingbrook 2.6 NE           4.00 in   0800 AM 08/19   COCORAHS             

...Grundy County...
Minooka                      4.74 in   0800 AM 08/19   COCORAHS             

...Kane County...
Aurora                       6.05 in   1009 AM 08/19   CWOP                 
Sugar Grove 1 NNW            5.67 in   0700 AM 08/19   COCORAHS             
North Aurora 2 SW            5.49 in   0800 AM 08/19   COCORAHS             
Aurora 2 W                   5.43 in   0700 AM 08/19   COCORAHS             
Montgomery - Blackberry Cr.  5.37 in   0930 AM 08/19   MESONET                 
Batavia 3.4 WSW              4.82 in   0600 AM 08/19   COCORAHS             
Aurora                       4.64 in   0700 AM 08/19   COOP                 
North Aurora                 4.53 in   0735 AM 08/19   COCORAHS             

...Kendall County...
Oswego                       8.54 in   0505 AM 08/19   COCORAHS             
Oswego                       7.61 in   1000 AM 08/19   CWOP                 
Oswego 3 NW                  7.56 in   0700 AM 08/19   COCORAHS             
Oswego 1 SSE                 7.36 in   0600 AM 08/19   COCORAHS             
Boulder Hill                 6.74 in   0615 AM 08/19   COCORAHS             
Boulder Hill 1 NNE           6.71 in   0700 AM 08/19   COCORAHS             
Plainfield 4 SW              6.19 in   0700 AM 08/19   COCORAHS             
Yorkville 4.5 N              5.66 in   0700 AM 08/19   COCORAHS             
Yorkville 0.9 SSW            5.42 in   0700 AM 08/19   COCORAHS             
Yorkville 3.1 N              5.15 in   0643 AM 08/19   COCORAHS             
Yorkville 3.0 N              4.97 in   0740 AM 08/19   COCORAHS             
Yorkville 1.7 SSE            4.68 in   0700 AM 08/19   COCORAHS             
Yorkville 1.0 N              4.36 in   0700 AM 08/19   COCORAHS             

...Lee County...
Paw Paw 2 S                  6.13 in   0700 AM 08/19   COOP                 
West Brooklyn 4.3 WNW        4.02 in   0800 AM 08/19   COCORAHS             

...McHenry County...
Bull Valley 2 WNW            5.53 in   0800 AM 08/19   COCORAHS             
Harvard 4.4 NNE              5.16 in   0633 AM 08/19   COCORAHS             
Woodstock 4 SW               4.84 in   0745 AM 08/19   COCORAHS             

...Will County...
Lockport - Chicago Ship Cana 6.71 in   0915 AM 08/19   MESONET                 
Rockdale 1 NW                6.62 in   0700 AM 08/19   COCORAHS             
Shorewood                    6.56 in   0700 AM 08/19   COCORAHS             
2 NW Plainfield              6.51 in   1005 AM 08/19   CWOP                 
Plainfield 3 NNW             6.35 in   0700 AM 08/19   COCORAHS             
Joliet 3 WNW                 6.09 in   0700 AM 08/19   COCORAHS             
Joliet 2.7 NW                6.06 in   0600 AM 08/19   COCORAHS             
2 NW Plainfield              6.00 in   0700 AM 08/19   COCORAHS             
Plainfield 3 ESE             5.94 in   0900 AM 08/19   COCORAHS             
Mokena 4 WNW                 5.88 in   0600 AM 08/19   COCORAHS             
Joliet 0.8 E                 5.72 in   0600 AM 08/19   COCORAHS             
Homer Glen 1 NNE             5.72 in   0600 AM 08/19   COCORAHS             
Mokena 1 W                   5.64 in   0700 AM 08/19   COCORAHS             
Plainfield 3.9 SSW           5.55 in   0605 AM 08/19   COCORAHS             
Plainfield 1.7 WNW           5.42 in   0700 AM 08/19   COCORAHS             
Shorewood - DuPage R.        5.39 in   0945 AM 08/19   MESONET                 
Mokena 2 SW                  5.38 in   0700 AM 08/19   COCORAHS             
New Lenox 2 NE               5.32 in   0800 AM 08/19   COCORAHS             
Romeoville - NWS Chicago     5.31 in   0700 AM 08/19   NWS OBS                 
Naperville 5 SSW             5.31 in   0700 AM 08/19   COCORAHS             
Plainfield 2 SSE             5.22 in   0700 AM 08/19   COCORAHS             
Homer Glen 2 NNE             5.19 in   0700 AM 08/19   COCORAHS             
Mokena 2 WSW                 4.88 in   0700 AM 08/19   COCORAHS             
Naperville 4 S               4.59 in   0700 AM 08/19   COCORAHS             
Crete 3 ENE                  4.51 in   0700 AM 08/19   COCORAHS             
Crete 3 E                    4.43 in   0700 AM 08/19   COCORAHS             
New Lenox 1 SSE              4.37 in   0700 AM 08/19   COCORAHS             
Naperville 4 SE              4.35 in   0800 AM 08/19   COCORAHS             
DuPage R. near Plainfield    4.29 in   0945 AM 08/19   MESONET                 
Frankfort 1 ESE              4.28 in   0700 AM 08/19   COCORAHS             
New Lenox 1 SE               4.27 in   0800 AM 08/19   COCORAHS             

...Winnebago County...
South Beloit 2 SE            5.12 in   0700 AM 08/19   COCORAHS             

...Indiana...

...Lake County...
Dyer - Hart Ditch            6.59 in   1000 AM 08/19   MESONET                 
Hammond 2 N                  6.37 in   0600 AM 08/19   COCORAHS             
Gary 5.9 ENE                 6.09 in   0700 AM 08/19   COCORAHS             
Gary 5 ENE                   5.76 in   0700 AM 08/19   COCORAHS             
Munster - Hart Ditch         5.72 in   1000 AM 08/19   MESONET                 
Hobart 1.1 S                 5.23 in   0700 AM 08/19   COCORAHS             
Gary 6.2 ENE                 5.08 in   0800 AM 08/19   COCORAHS             
Highland 1 SW                4.98 in   0700 AM 08/19   COCORAHS             
Hobart 2.4 SE                4.67 in   0830 AM 08/19   COCORAHS             
Dyer                         4.31 in   0800 AM 08/19   COCORAHS             
Munster - Little Calumet R.  4.29 in   1000 AM 08/19   MESONET                 
2 SE Tinley Park             4.15 in   0955 AM 08/19   CWOP                 

...Porter County...
Ogden Dunes                  6.28 in   0555 AM 08/19   COCORAHS             
Portage 3 E                  5.50 in   0700 AM 08/19   COCORAHS             
Lakes of the Four Seasons    4.48 in   0830 AM 08/19   COCORAHS             
Valparaiso 2.8 W             4.05 in   0810 AM 08/19   COCORAHS             
Porter                       4.03 in   0700 AM 08/19   COCORAHS             

Observations are collected from a variety of sources with varying
equipment and exposures. We thank all volunteer weather observers 
for their dedication. Not all data listed are considered official.

$$

 

                                                           For more information on the events of August 16th and 17th can be found here

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Additional event recaps can be found on the NWS Chicago Past Events Page		 nws logo

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