August 7-8, 2022: Two Rounds of Heavy Rain Over 30 Hours Produce Over 5" of Rainfall and Flash Flooding

Fast Facts

• Two bouts of heavy rainfall occurred across northern Illinois on the mornings of August 7 and August 8, with combined totals as high as 4 to 7 inches in Winnebago, Ogle, Lee, and DeKalb Counties in far northern Illinois. Northwest Illinois, namely Stephenson County, saw even higher totals with over 10 inches of rain occurring in and near Freeport.

• A near tropical environment (as felt at the surface with around 80° dew points!) supported very heavy rainfall rates of >2 inches per hour, and this resulted in flash flooding across portions of far northern Illinois, including Rockford, Polo, Byron, and Oregon.

• Rockford's official 2-day total, as measured by the weather observer at the Chicago-Rockford International Airport, was 6.15". This was the highest 2-day precipitation total in Rockford since July 23-24, 2010 (7.51"), and was the first time since that 2010 event when two consecutive calendar days with 2"+ of rainfall occurred there. It was also the first day with over 3" of rain in Rockford since June 28, 2017, which saw 4.11" of rain.

Rockford rainfall facts

August 7-8 Rainfall Reports

Public Information Statement
National Weather Service Chicago IL
1239 PM CDT Tue Aug 9 2022 /139 PM EDT Tue Aug 9 2022/

...Two Inch Plus Rainfall Amounts from Sat Night Aug 6 through 
Mon Aug 8...

Location                     Amount    Time/Date       Provider

...Illinois...

...Boone County...
Timberlane 1 SW              3.85 in   0700 AM 08/09   COCORAHS
Capron                       3.06 in   0700 AM 08/09   COCORAHS

...Cook County...
Oak Forest 1 NNW             3.26 in   0700 AM 08/09   COCORAHS
Hoffman Estates 2 WNW        2.15 in   1000 AM 08/09   COCORAHS

...De Kalb County...
NIU Agronomy Shabonna 5 NNE  4.72 in   1100 AM 08/09   HADS
Genoa                        4.32 in   0700 AM 08/09   COOP
DeKalb (NIU)                 4.30 in   0700 AM 08/09   COOP
Malta 3 ESE                  4.25 in   0700 AM 08/09   COCORAHS
DeKalb                       3.94 in   0700 AM 08/09   COCORAHS
Cortland                     3.43 in   0600 AM 08/09   COCORAHS
Earlville 5 NNE              2.33 in   0600 AM 08/09   COCORAHS

...Kane County...
Batavia 3.4 WSW              3.03 in   0600 AM 08/09   COCORAHS
Elgin                        2.37 in   0700 AM 08/09   COOP
Geneva 4 WSW                 2.35 in   0400 AM 08/09   COCORAHS
Batavia                      2.26 in   0600 AM 08/09   UCOOP
Elgin 8 WSW                  2.15 in   0700 AM 08/09   COCORAHS
Batavia 1 NW                 2.14 in   0640 AM 08/09   COCORAHS

...La Salle County...
Mendota 1 SE                 3.36 in   0700 AM 08/09   COOP
Earlville 3 S                2.57 in   0600 AM 08/09   COOP

...Lee County...
Dixon 3 NNW                  4.98 in   0730 AM 08/09   COCORAHS
Amboy 1 WSW                  4.71 in   0542 AM 08/09   COCORAHS
Dixon 1 NE                   4.38 in   0700 AM 08/09   COCORAHS
Dixon                        4.30 in   0700 AM 08/09   COOP
Nelson 3 NNW                 3.75 in   0800 AM 08/09   COCORAHS
Ashton                       3.36 in   0700 AM 08/09   COCORAHS
Steward 3 S                  3.08 in   0700 AM 08/09   COOP
Paw Paw 2 S                  2.76 in   0700 AM 08/09   COOP
Sublette 3 WNW               2.33 in   0700 AM 08/09   COCORAHS

...McHenry County...
Harvard                      2.50 in   0700 AM 08/09   COOP
Marengo                      2.01 in   0700 AM 08/09   COCORAHS

...Ogle County...
Forreston                    6.69 in   1200 AM 08/09   MESONET
Byron                        4.99 in   1200 AM 08/09   MESONET
Rochelle Airport             4.40 in   1055 AM 08/09   AWOS

...Will County...
New Lenox 2 NE               3.88 in   0800 AM 08/09   COCORAHS
Homer Glen 3 S               3.75 in   0700 AM 08/09   COCORAHS
Mokena 2 WSW                 3.37 in   0700 AM 08/09   COCORAHS
New Lenox 2 SW               3.13 in   0700 AM 08/09   COCORAHS
Homer Glen 2 NNE             2.86 in   0700 AM 08/09   COCORAHS
New Lenox 1 SSE              2.77 in   0700 AM 08/09   COCORAHS
Homer Glen 1 NNE             2.10 in   0700 AM 08/09   COCORAHS

...Winnebago County...
New Milford 3 W              6.94 in   0700 AM 08/09   COCORAHS
Rockford Airport             6.15 in   0700 AM 08/09   ASOS
Winnebago 5 SE               5.77 in   0625 AM 08/09   COCORAHS
Rockford 3 WSW               5.52 in   0700 AM 08/09   COCORAHS
4 NNW Rockford               5.00 in   0700 AM 08/09   COCORAHS
Machesney Park 1 NW          4.90 in   0500 AM 08/09   COCORAHS
Rockton 3.1 SW               4.18 in   0630 AM 08/09   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.

$$

RC

Flooding & Local Storm Reports

The below reports are local storm reports, including flooding,
received during or shortly after the event. More detailed flash 
flood reports were received in the weeks after the event from Ogle
County. These included a sinkhole developing near Illinois Route 2
south of Oregon, with some associated structural damage, as well as
dozens of homes with flood damage in Polo. More finalized detailed 
storm reports from those below will be able to be found on our 
Storm Data page.



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

0100 PM     FLASH FLOOD      1 SSW OAK FOREST        41.59N 87.75W
08/07/2022                   COOK               IL   LAW ENFORCEMENT  

            167TH STREET CLOSED DUE TO FLOODING. SIDE 
            ROADS LIKELY FLOODED AS WELL.

0126 PM     TSTM WND DMG     3 E KOUTS               41.32N 86.98W
08/07/2022                   PORTER             IN   PUBLIC           

            POWER LINE DOWNED EAST OF KOUTS ON COUNTY 
            ROAD 450 E NORTH OF THE INTERSECTION WITH 
            STATE ROUTE 8. TIME ESTIMATED FROM RADAR. 

0130 PM     FLASH FLOOD      MIDLOTHIAN              41.63N 87.72W
08/07/2022                   COOK               IL   LAW ENFORCEMENT  

            POLICE DEPARTMENT REPORTED WATER OVER KARLOV 
            AVENUE. TIME IS ESTIMATED FROM RADAR.

0452 AM     FLASH FLOOD      2 ESE ROCKFORD          42.26N 89.05W
08/08/2022                   WINNEBAGO          IL   PUBLIC           

            PHOTOS AND VIDEOS SHOW KEITH CREEK AT 
            BANKFULL NEAR SHOPPING CENTER AT CHARLES 
            STREET AND HUNTER AVENUE IN ROCKFORD. 
            RELAYED BY ROCKFORD SCANNER. 

0530 AM     FLASH FLOOD      1 ENE BYRON             42.13N 89.25W
08/08/2022                   OGLE               IL   911 CALL CENTER  

            STANDING WATER AT IL-2 RAILROAD UNDERPASS 
            BEGAN AROUND 530 AM, THEN WORSENED TO NEARLY 
            4 FEET IN DEPTH BY 630 AM TO 700 AM. RELAYED 
            BY OGLE COUNTY DISPATCH. 

0530 AM     FLASH FLOOD      1 E ROCKFORD            42.27N 89.07W
08/08/2022                   WINNEBAGO          IL   LAW ENFORCEMENT  

            LAW ENFORCEMENT HAS RECEIVED MULTIPLE 
            REPORTS OF FLOODED INTERSECTION. 

0635 AM     FLOOD            1 NNE DEKALB            41.95N 88.74W
08/08/2022                   DE KALB            IL   PUBLIC           

            MULTIPLE PUBLIC REPORTS OF STREET FLOODING 
            IN DEKALB AND SYCAMORE AREAS RELAYED VIA 
            MPING. 

0700 AM     LIGHTNING        ROCKFORD                42.27N 89.09W
08/08/2022                   WINNEBAGO          IL   FIRE DEPT/RESCUE 

            ROCKFORD FIRE DEPARTMENT INDICATES THAT 
            LIGHTNING IS LIKELY CAUSE OF FIRE AT CHURCH 
            NEAR PRAIRIE STREET AND 2ND STREET IN 
            ROCKFORD. 3 FIREFIGHTERS INJURED WHILE 
            FIGHTING THE FIRE. RELAYED BY ROCKFORD 
            REGISTER STAR.

0800 AM     FLASH FLOOD      3 ESE ROCKFORD          42.25N 89.04W
08/08/2022                   WINNEBAGO          IL   LAW ENFORCEMENT  

            BROADWAY AND EASTMORELAND AVENUE REMAINS 
            CLOSED DUE TO FLOODING FROM EARLIER HEAVY 
            RAINFALL. RELAYED VIA BROADCAST MEDIA. 

0800 AM     FLASH FLOOD      4 WSW CHERRY VALLEY     42.22N 89.03W
08/08/2022                   WINNEBAGO          IL   LAW ENFORCEMENT  

            SANDY HOLLOW ROAD AND ALPINE ROAD REMAINS 
            CLOSED DUE TO FLOODING FROM EARLIER HEAVY 
            RAINFALL. RELAYED VIA BROADCAST MEDIA. 

0820 AM     FLOOD            WINNEBAGO               42.27N 89.24W
08/08/2022                   WINNEBAGO          IL   PUBLIC           

            SOME BACKYARDS UNDER NEARLY 1 FOOT OF WATER. 
            WIDESPREAD BASEMENT FLOODING. REPORT RELAYED 
            TWITTER.

0820 AM     FLASH FLOOD      2 SSW CHERRY VALLEY     42.22N 88.98W
08/08/2022                   WINNEBAGO          IL   TRAINED SPOTTER  

            CORRECTION TO PREVIOUS FLOOD REPORT FROM 3 
            NNE NEW MILFORD. SMALL, TYPICALLY DRY DITCH 
            OUT OF ITS BANKS NEAR LINDEN ROAD AND BROOK 
            DALE ROAD. VIDEO OF FLOODING ALSO RELAYED BY 
            BROADCAST MEDIA. 

1042 AM     FLASH FLOOD      POLO                    41.98N 89.58W
08/08/2022                   OGLE               IL   FIRE DEPT/RESCUE 

            STANDING WATER INSIDE THE POLO FIRE 
            PROTECTION DISTRICT STATION. KNEE DEEP WATER 
            OUTSIDE IN THE YARD. TIME BASED OFF REPORT 
            TIME VIA NWSCHAT.

Additional Info

7 A.M. NWS Quad Cities weather balloon data from August 7 (left) and August 8 (right). These sampled 2.32" and 2.37" of precipitable water, respectively, which were both top ten observations for the month of August for NWS Quad Cities (1995-present). This incredibly rich moisture, as well as a low-level jet providing ample moisture replenishment, resulted in efficient rain-production in showers and storms.

• Northwest Illinois Event Page (NWS Quad Cities)
• NWS Chicago Past Events Page