Severe thunderstorms moved across parts of northern Illinois during the afternoon hours of August 16th.
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.
Severe thunderstorms moved across parts of northern Illinois during the afternoon hours of August 16th.
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 16, 12:13 PM CST, 47 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL 113 PM CDT SUN AUG 16 2009 .DISCUSSION... 109 PM CDT THIS AFTERNOON...AFTER MODIFYING THE DVN SOUNDING THERE IS FORECAST 2,396 J/KG OF CONVECTIVE AVAILABLE ENERGY. THERE WILL BE THUNDERSTORMS THIS AFTERNOON. THE ACARS SOUNDING SHOWS 970 TO 1500 J/KG FROM THE MODIFIED ACARS SOUNDING. A LARGE AREA OF DEWPOINTS OF 72 DEGREES MOVING INTO NORTH CENTRAL ILLINOIS FROM CENTRAL ILLINOIS. THE SOUTH WIND WILL INCREASE THIS AFTERNOON. THERE WILL BE SOME CONVERGENCE WITH THE INCREASE WIND SPEED AND THE INSTABILITY WILL BE ENOUGH FOR THUNDERSTORMS THIS AFTERNOON. && .PREV DISCUSSION... 247 AM CDT FOCUS IS IN THE SHORT TERM TODAY THRU MONDAY. STAGE HAS BEEN SET UP TO EXPECT THE SHOWERS AND TSTMS WEST OF THE MS RVR TO WORK INTO ILLINOIS TODAY. WITH THE HIGH PRESSURE RIDGE NOW OFF THE EAST COAST AND CONTINUING TO DEPART...THE LLJ FEEDING THE CURRENT ACTIVITY IN IOWA WITH DEEP GULF MSTR SHUD SHIFT ACROSS THE RVR THIS MRNG AND INVADE NW IL. CONTINUED PROGRESS ACROSS IL TODAY SHUD SPREAD TSTMS INTO NERN IL BY AFTN. AM MAINTAINING LIKELY POPS BUT EXPECT CATEGORICAL VALUES ACROSS SRN WI AND PERHAPS EXTENDING SW INTO NORTHWEST IL AS WELL. HIGH POPS EXPECTED ALL CWA TONIGHT. THE LLJ TO 40 KTS FEEDING MOISTURE UP THRU NRN IL TODAY WILL SHIFT EAST INTO NW INDIANA TONIGHT. PRECIPITABLE WATER VALUES REMAIN NEAR 2 INCHES AND WITH SLOW PROGRESS EAST AS A RESULT OF WEAK MID LVL FLOW...MAY BE SOME TRAINING OF STORMS DUMPING ISOLATED SPOTS OF 3 TO 4 INCHES BETWEEN THIS AFTN AND MONDAY MRNG. SUBSEQUENT FLOODING MAY RESULT DEPENDING ON RESPITES BETWEEN STORMS. DAYTIME HEATING INTO THE MID AND UPR 80S SHUD FORCE CAPES TO 1200 JOULES THIS AFTN. EXPECTING MOST SUNSHINE TO OCCUR EARLY IN THE DAY AND CLOUDING UP NEAR THE CONVECTIVE TEMP AROUND 85 WHEN EXPECT THERMAL BUOYANCY TO BREAK THRU THE LFC. THIS CONVECTIVE THREAT CONTINUES THRU MONDAY...TERMINATING LATE MON NGT INTO TUESDAY MRNG WITH FROPA. WELL ORGANIZED UPPER LOW RIDING ACROSS SRN CANADA SHUD MOVE FROM SRN MANITOBA INTO SRN ONTARIO OVERNIGHT MON NGT AND SWING A COLD FRONT DOWN THRU NRN IL BY MRNG. THIS FRONT GETTING CAUGHT IN WESTERLY LAMINAR FLOW ALOFT AND QUESTION ARISES AS TO HOW FAR THIS FRONT DROPS SOUTH BFR USHERING MSTR BACK NORTH WITH THE NEXT WAVE FROM THE SW RIDING ALONG THIS BOUNDARY. MODELS TEND TO DEEPEN MID LVL FLOW EARLY WED IN THE PLAINS AND RIDE THIS WAVE ACROSS IL DURING THE DAY. TSTM CHANCES REMAIN IN THE PICTURE FROM WED THRU THURS NIGHT WHEN ANOTHER MAJOR TROF SLIPS ACROSS SRN CANADA AND SWINGS A COLD FRONT THRU BY FRI MRNG. WEEKEND IS EXPECTED TO SEE COOLER TO MORE SEASONABLE TEMPS AFTER THIS FRONTAL PASSAGE. GFS STILL SEEMS A BIT MORE AGGRESSIVE AND AM LEANING MORE FAVORABLY TO THE NAM AND ECMWF. HAVE MADE LITTLE CHANGES TO TEMPS. TIMING OF INCREASING CLOUDINESS AND FREQUENCY AND LENGTH OF RAIN WILL VARY MAX TEMPS TODAY AND MONDAY. RLB && .AVIATION... 1800 UTC TAFS...MANY DIFFERENT FACTORS...INCLUDING A LOW LEVEL JET...MOISTURE CONVERGENCE WITH 70+ SFC DEWPOINTS...UPPER LEVEL SHORTWAVES...AFTERNOON HEATING AND AN APPROACHING SURFACE TROF...ARE SUPPORTING THE SHOWERS AND THUNDERSTORMS MOVING ACROSS THE AREA THIS AFTERNOON. DESPITE THE DESIRE TO GET REALLY PRECISE WITH THE EVOLUTION OF THIS ACTIVITY...THE GENERAL TREND WILL BE FOR THUNDERSTORMS TO BECOME MORE WIDESPREAD AS THE AFTERNOON PROGRESSES. THERE COULD BE A BREAK IN THE PRECIP THIS EVENING AFTER THE DAYTIME HEATING WANES AND BEFORE THE LARGER SCALE FORCING TAKES OVER. WITH SO MUCH GOING ON THIS AFTERNOON AND OVERNIGHT...HAVE NOT ADDED SIGNIFICANT DETAILS FOR TOMORROW YET BUT ANTICIPATE CONTINUED RAIN AND SHOWER ACTIVITY INTO MONDAY NIGHT BEFORE THE MAIN COLD FRONT PASSES. LENNING && .MARINE... 319 AM CDT LOW PRESSURE CURRENTLY LOCATED OVER THE NORTHERN PLAINS WILL SLOWLY MOVE NORTHEAST INTO SOUTHERN CANADA ON SUNDAY. AS THIS OCCURS...SOUTHERLY WINDS WILL BE MAINTAINED ACROSS MUCH OF THE LAKE. THIS LOW PRESSURE WILL CONTINUE TO TRACK EAST THROUGH ONTARIO ON MONDAY...WEAKENING AS IT PROGRESSES EAST. WITH THIS EASTWARD PROGRESSION THROUGH MONDAY EVENING...A COLD FRONT EXTENDING SOUTHWEST FROM THIS LOW WILL MOVE ACROSS THE LAKE BRINGING A RETURN TO MORE OF A WESTERLY COMPONENT TO THE WINDS. DURING THIS TIME FRAME...A RIDGE OF HIGH PRESSURE WILL REMAIN NEARLY STATIONARY ACROSS THE EAST COAST THROUGH THE MIDDLE PART OF THE WEEK. RODRIGUEZ && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...NONE. &&
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL 1132 AM CDT SUN AUG 16 2009 ILZ003>006-008-010>014-019>023-032-033-039-INZ001-002-010-011-019- 171645- WINNEBAGO-BOONE-MCHENRY-LAKE ILLINOIS-OGLE-LEE-DE KALB-KANE- DUPAGE-COOK-LA SALLE-KENDALL-GRUNDY-WILL-KANKAKEE-LIVINGSTON- IROQUOIS-FORD-LAKE INDIANA-PORTER-NEWTON-JASPER-BENTON- 1132 AM CDT SUN AUG 16 2009 /1232 PM EDT SUN AUG 16 2009/ THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH CENTRAL ILLINOIS... NORTHEAST ILLINOIS AND NORTHWEST INDIANA. .DAY ONE...TODAY AND TONIGHT. WEATHER HAZARDS EXPECTED: THERE WILL BE THUNDERSTORMS. THERE WILL BE CLOUD TO GROUND LIGHTNING. THE RAINFALL MAY REACH A HALF AN INCH PER HOUR IN SOME THUNDERSTORMS THIS EVENING AND TONIGHT. AREAS AFFECTED AND TIMING: NORTH CENTRAL ILLINOIS AFTER 3 PM CDT. THEN NORTHEAST ILLINOIS AND NORTHWEST INDIANA LATER THIS AFTERNOON AND THIS EVENING. DISCUSSION: SOME SHOWERS AND ISOLATED THUNDERSTORMS WILL REACH NORTHEAST ILLINOIS THIS AFTERNOON. THE THUNDERSTORMS WITH HEAVY RAIN WILL REACH NORTHEAST ILLINOIS AND NORTHWEST INDIANA LATE THIS AFTERNOON AND EVENING. THESE THUNDERSTORMS WILL BE ALONG A 850 MB CONVERGENCE AREA AT THE FRONT OF A JET STREAK AT THAT LEVEL. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY. THUNDERSTORMS WILL CONTINUE THROUGH MONDAY INTO MONDAY NIGHT. ANOTHER THREAT OF THUNDERSTORMS IS EXPECTED TUESDAY NIGHT THROUGH THURSDAY NIGHT. .SPOTTER INFORMATION STATEMENT... SPOTTERS SHOULD REPORT ANY HEAVY RAINFALL OR MINOR FLOODING LATE TODAY AND TONIGHT. && COMPLETE FORECAST INFORMATION IS AVAILABLE ON THE NWS CHICAGO WEBPAGE: WEATHER.GOV/CHICAGO LMZ740>745-171645- WINTHROP HARBOR TO WILMETTE HARBOR- WILMETTE HARBOR TO NORTHERLY ISLAND- NORTHERLY ISLAND TO CALUMET HARBOR-CALUMET HARBOR TO GARY- GARY TO BURNS HARBOR-BURNS HARBOR TO MICHIGAN CITY- 1132 AM CDT SUN AUG 16 2009 THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE ILLINOIS NEARSHORE WATERS OF LAKE MICHIGAN AND THE INDIANA NEARSHORE WATERS OF LAKE MICHIGAN. .DAY ONE...TODAY AND TONIGHT. THUNDERSTORMS WILL MOVE INTO THE NEAR SHORE OF ILLINOIS AND INDIANA LATE THIS AFTERNOON AND EVENING. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY. THUNDERSTORMS ARE AGAIN PROBABLE MONDAY AND MONDAY NIGHT AND AGAIN WEDNESDAY THROUGH FRIDAY. && COMPLETE FORECAST INFORMATION IS AVAILABLE ON THE NWS CHICAGO WEBPAGE: WEATHER.GOV/CHICAGO LMZ080-261-362-364-366-563-565-567-669-671-673-675-777-779-868- 870-872-874-876-878-171645- LAKE MICHIGAN FROM MICHIGAN CITY IN TO ST. JOSEPH MI 5 NM OFFSHORE TO MID LAKE- LAKE MICHIGAN FROM SEUL CHOIX POINT TO ROCK ISLAND PASSAGE 5 NM OFFSHORE TO MID LAKE- LAKE MICHIGAN SOUTH OF A LINE FROM SEUL CHOIX POINT TO THE MACKINAC BRIDGE AND NORTH OF A LINE FROM CHARLEVOIX MI TO SOUTH FOX ISLAND 5 NM OFFSHORE- LAKE MICHIGAN FROM CHARLEVOIX TO POINT BETSIE MI 5 NM OFFSHORE TO MID LAKE- LAKE MICHIGAN FROM POINT BETSIE TO MANISTEE MI 5 NM OFFSHORE TO MID LAKE- LAKE MICHIGAN FROM ROCK ISLAND PASSAGE TO STURGEON BAY WI- LAKE MICHIGAN FROM STURGEON BAY TO TWO RIVERS WI 5 NM OFFSHORE TO MID LAKE- LAKE MICHIGAN FROM TOW RIVERS TO SHEBOYGAN WI 5 NM OFFSHORE TO MID LAKE- LAKE MICHIGAN FROM SHEBOYGAN TO PORT WASHINGTON WI 5 NM OFFSHORE TO MID LAKE- LAKE MICHIGAN FROM PORT WASHINGTON TO NORTH POINT LIGHT WI 5 NM OFFSHORE TO MID LAKE- LAKE MICHIGAN FROM NORTH POINT LIGHT TO WIND POINT WI 5 NM OFFSHORE TO MID LAKE- LAKE MICHIGAN FROM WIND POINT WI TO WINTHROP HARBOR IL 5 NM OFFSHORE TO MID LAKE- LAKE MICHIGAN FROM WINTHROP HARBOR TO WILMETTE HARBOR IL 5 NM OFFSHORE TO MID LAKE- LAKE MICHIGAN FROM WILMETTE HARBOR IL TO MICHIGAN CITY IN 5 NM OFFSHORE TO MID LAKE- LAKE MICHIGAN FROM PENTWATER TO MANISTEE MI 5 NM OFFSHORE TO MID LAKE- LAKE MICHIGAN FROM WHITEHALL TO PENTWATER MI 5 NM OFFSHORE TO MID LAKE- LAKE MICHIGAN FROM GRAND HAVEN TO WHITEHALL MI 5 NM OFFSHORE TO MID LAKE- LAKE MICHIGAN FROM HOLLAND TO GRAND HAVEN MI 5 NM OFFSHORE TO MID LAKE- LAKE MICHIGAN FROM SOUTH HAVEN TO HOLLAND MI 5 NM OFFSHORE TO MID LAKE- LAKE MICHIGAN FROM ST. JOSEPH TO SOUTH HAVEN MI 5 NM OFFSHORE TO MID LAKE- 1132 AM CDT SUN AUG 16 2009 THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE OPEN WATERS OF LAKE MICHIGAN. .DAY ONE...TODAY AND TONIGHT. THUNDERSTORMS WILL MOVE INTO LAKE MICHIGAN LATE THIS AFTERNOON AND TONIGHT. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY. THUNDERSTORMS ARE AGAIN POSSIBLE OVER LAKE MICHIGAN MONDAY AND MONDAY NIGHT AND WEDNESDAY THROUGH SATURDAY. && COMPLETE FORECAST INFORMATION IS AVAILABLE ON THE NWS CHICAGO WEBPAGE: WEATHER.GOV/CHICAGO
The Chicago radar (KLOT), 33 km away, was scanning. The volume nearest the first event began at 19:02 UTC.
6 thunderstorm wind, 1 heavy rain. Local standard time, as filed.
Large tree limbs and signs were blown down along Route 30 between Route 47 and Route 25.
A wind gust to 62 mph was measured near Route 30 and Route 25.
One inch of rain fell in 30 minutes in Batavia.
A 20 foot tall tree was blown down.
A wind gust was measured to 62 mph.
A wind gust was measured to 58 mph.
An 8 to 10 inch diameter tree limb was blown down blocking the roadway near 114th Street and New England Street.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Illinois in 2009Every state in 2009This day in weather historyWarnings in Illinois, August 2009
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 2026-09-24. Each event’s entry at NCEI: 193841, 193840, 193837, 193836, 193838, 193839, 193842.