Severe thunderstorms developed during the afternoon hours and moved northeast across parts northern and central Illinois. Three tornadoes were confirmed during this event.
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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 developed during the afternoon hours and moved northeast across parts northern and central Illinois. Three tornadoes were confirmed during this event.
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 19, 2:16 PM CST, 49 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL 316 PM CDT WED AUG 19 2009 .DISCUSSION... 238 PM...MAIN CONCERNS THIS AFTERNOON ARE SVR WEATHER AND TORNADO THREAT THRU THIS EVENING AS A WARM FRONT LIFTS NORTH...AND THEN POTENTIAL FOR HEAVY RAIN AND FLOODING OVERNIGHT INTO THURSDAY MORNING. COMPLEX AND DIFFICULT SITUATION TO FORECAST OVER THE NEXT 12-18 HRS. CONVECTION WHICH MOVED INTO WESTERN IL ASSOCIATED WITH AN MCV AS BEGUN TO STRENGTHEN IN THE PAST FEW HRS AND IS NOW RESEMBLING MORE OF A SQUALL LINE. APPEARS TO BE TWO WARM FRONTS OR A MOISTURE FRONT/BOUNDARY...WHERE DEWPOINTS JUMP FROM THE 60S TO THE 70S... WHICH IS ENTERING THE SOUTHERN PART OF THE CWA AND THEN THE MAIN WARM FRONT IS STILL ACROSS CENTRAL IL WHERE TEMPS JUMP FROM THE LOWER 80S TO NEAR 90. THE THREAT OF TORNADOES WILL BEGIN TO DIMINISH WITH SUNSET AND LOSS OF DAYTIME HEATING...IN ADDITION TO THE WARM FRONT POSSIBLY BEING NORTH OF THE CWA BY THEN. WHILE RECENT AND CURRENT CONVECTIVE/RADAR TRENDS SUGGEST A LINE OF STORMS...CANNOT RULE OUT INDIVIDUAL STORMS/SUPERCELLS EITHER AHEAD OF THE CURRENT LINE OR DEVELOPING TO THE SOUTHWEST OF THE EXISTING LINE AND THEN LIFTING NORTHEAST. CERTAINLY ANYTHING THAT DEVELOPS NEAR OR ALONG THE WARM FRONT WILL HAVE THE POTENTIAL TO SPIN A TORNADO. CURRENT TORNADO WATCH HAS THE AREA OF CONCERN HIGHLIGHTED FOR NOW BUT WILL NEED TO MONITOR HOW FAR NORTH AND ESPECIALLY EAST THE CONVECTION DEVELOPS AND MOVES OVER THE NEXT FEW HRS. THIS ACTIVITY IS EXPECTED TO DIMINISH BY EARLY/MID EVENING AND EXPECT A RELATIVELY QUIET PERIOD THRU LATE EVENING BEFORE ANOTHER SHORTWAVE...OR TWO...MOVES ACROSS THE REGION OVERNIGHT INTO THURSDAY MORNING. BOTH THE ECMWF AND THE GFS SEEM TO AGREE IN PUSHING THE THREAT OF HEAVY RAIN OVERNIGHT FURTHER SOUTH ACROSS CENTRAL IL AND CENTRAL INDIANA. HPC QPF FORECASTS ALSO FOLLOW THIS THINKING AND WILL TREND HEAVY RAIN MENTION FURTHER SOUTH. WITH PRECIPITABLE WATER VALUES AROUND 2 INCHES...DURATION OF HEAVY RAINFALL WHICH MAY ONLY BE A FEW HRS COULD LEAD TO LOCALIZED FLOODING AND PERHAPS SOME ISOLATED FLASH FLOODING. BY THURSDAY AFTERNOON...CWA IS DRY SLOTTED AS THE VERTICALLY STACKED LOW LIFTS NORTHEAST ACROSS THE NORTHERN LAKES. SO HAVE TRIMMED BACK POPS BY THURS AFTERNOON LEAVING JUST A SLIGHT CHANCE ACROSS MOST OF THE CWA. WRAP AROUND INSTABILITY SHOWERS DEVELOP FRIDAY MORNING AND LAST THRU EARLY EVENING. EXPECTED CLOUD COVER ALONG WITH ISOLATED SHOWERS WILL LIKELY LEAD TO A RATHER COOL MID AUGUST DAY WITH HIGHS ONLY IN THE LOWER/MID 70S AND THAT MIGHT BE GENEROUS DEPENDING ON ANY SUNSHINE OR LACK THEREOF IN THE MORNING. HIGH PRESSURE BUILDS ACROSS THE REGION THIS WEEKEND WITH DRY WEATHER EXPECTED UNTIL NEXT TUESDAY NIGHT OR WEDNESDAY WHEN A COLD FRONT MOVES SOUTH ACROSS THE LAKES. TEMPERATURES OVER THE WEEKEND SLIGHTLY BELOW NORMAL IN THE MID/UPPER 70S...BUT TEMPS WARM EARLY NEXT WEEK ON THE BACK SIDE OF THE HIGH WITH MID 80S POSSIBLE BY TUESDAY. CMS && .AVIATION... 100 PM CDT 1800 UTC TAFS...WARM FRONT DRAPED OUT ACROSS CENTRAL IL WITH STRONG SURGE OF LOW LEVEL MOISTURE/WARM ADVECTION HEADED NORTHWARD INTO THE LOCAL AREA WITH THE FRONT EXPECTED THIS AFTERNOON. CONCERN FOR WEAK SPIN UP TORNADOES WITH BACKED LOW LEVEL FLOW NORTH OF THE BOUNDARY ENHANCING LOW LEVEL SHEAR. EXPECT ONGOING CONVECTION CURRENTLY MOVING INTO WESTERN IL AS OF 18Z TO CONTINUE TO LIFT NNE WITH SOME REDEVELOPMENT EXPECTED AIDED BY DIURNAL HEATING AND RESULTING MARGINAL INSTABILITY. AS WARM FRONT LIFTS NORTH ACROSS THE AREA THIS AFTERNOON... BIGGEST CONCERN FOR TORNADOES WILL BE NEAR AND JUST TO THE COOL SIDE OF THE FRONT. EXPECT WARM FRONT TO LIFT NORTH OF IL-WI BORDER BY 00-01Z. WITH WARM FRONTAL PASSAGE EXPECT BREAK IN PRECIP WITH ONLY ISOLD SHWRS/TSTMS UNTIL MORE SIGNIFICANT AREA OF CONVECTION ASSOCIATED WITH RIGOROUS UPPER LEVEL TROUGH AND AHEAD OF APPROACHING COLD FRONT MOVES INTO THE AREA DURING THE OVERNIGHT HOURS. WITH COLD FRONT PASSAGE EARLY THURSDAY... RESIDUAL CYCLONIC FLOW COMBINED WITH COLD POOL ALOFT WITH ALLOW FOR INSTABILITY SHOWERS TO LINGER. EXPECT PATCHY IFR CONDITIONS OVERNIGHT WITH LARGE AREA OF PCPN WITH PATCHY MVFR VSBYS DUE TO FOG LINGERING INTO THE DAY THURSDAY. ED F && .MARINE... 315 PM CDT IMPRESSIVE 999 MB SURFACE LOW FOR TIME OF YEAR POISED TO PUSH EAST ACROSS UPPER MISSISSIPPI VALLEY INTO THE UPPER GREAT LAKES REGION TONIGHT THROUGH THURSDAY. STRONG PUSH OF LOW LEVEL MOISTURE/WARM AIR ADVECTION FROM THE SOUTH HELPING TO FUEL TSTMS TONIGHT BOTH AHEAD OF A WARM FRONT LIFTING NORTH AND ALONG AND AHEAD OF A COLD FRONT THAT WILL SWEEP EAST ACROSS THE AREA THURSDAY MORNING. STRONG COLD AIR ADVECTION (FOR AUGUST) BEHIND THE COLD FRONT LATER THURSDAY INTO FRIDAY RESULTS IN H85 (ABOUT 4500 FT UP) TEMPS LOWERING TO +6 DEG C BY FRIDAY NIGHT. THIS YIELDS A VERY UNSTABLE LOW LEVEL THERMAL PROFILE ACROSS LAKE MICHIGAN AIDING GOOD MIXING OF HIGHER MOMENTUM AIR TO THE SURFACE AND HIGHER WAVE GROWTH THEN TYPICALLY EXPERIENCED THIS TIME OF YEAR...EVEN FOR THE SAME WIND SPEED. PROXIMITY OF UPPER LEVEL LOW ACROSS THE WESTERN GREAT LAKES WILL RESULT IN UNSETTLED WX THROUGH FRI NIGHT BEFORE INCREASING DRYING AND RISING UPPER HEIGHTS WITH BUILDING SURFACE RIDGE BRINGS CALMER AND DRYER WEATHER LATER SATURDAY AND SUNDAY INTO MONDAY. ED F && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...NONE. &&
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL 1108 AM CDT WED AUG 19 2009 ILZ003>006-008-010>014-019>023-032-033-039-INZ001-002-010-011-019- 201615- 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- 1108 AM CDT WED AUG 19 2009 /1208 PM EDT WED AUG 19 2009/ THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH CENTRAL ILLINOIS... NORTHEAST ILLINOIS AND NORTHWEST INDIANA. .DAY ONE...TODAY AND TONIGHT. WEATHER HAZARDS EXPECTED: SCATTERED THUNDERSTORMS...THE STRONGEST MAY PRODUCE: ISOLATED TORNADOES. TORRENTIAL RAINFALL...POSSIBLY RESULTING IN FLASH FLOODING. SMALL HAIL. FREQUENT CLOUD TO GROUND LIGHTNING. AREAS AFFECTED...TIMING AND DISCUSSION: A WARM FRONT WILL MOVE NORTH ACROSS THE AREA THIS AFTERNOON INTO EARLY THIS EVENING. SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP ALONG AND AHEAD OF THIS WARM FRONT. THERE IS A CHANCE THAT SOME OF THESE THUNDERSTORMS MAY PRODUCE AN ISOLATED TORNADO. THE AREA WHERE A TORNADO IS MOST LIKELY WOULD BE WEST OF A LINE FROM MCHENRY TO PONTIAC THROUGH THIS EVENING. HEAVY RAIN IS ALSO POSSIBLE WITH SOME OF THE STRONGEST STORMS. ONCE THE WARM FRONT LIFTS NORTH INTO WISCONSIN...THE EVENING HOURS ARE EXPECTED TO BE QUIET. AS AN UPPER LEVEL DISTURBANCE APPROACHES THE AREA LATE TONIGHT...THUNDERSTORMS WILL ONCE AGAIN DEVELOP ACROSS THE AREA. THESE THUNDERSTORMS ARE EXPECTED TO PRODUCE VERY HEAVY RAIN WITH LOCALIZED AMOUNTS AS HIGH AS 2 INCHES BY THURSDAY MORNING. THIS HEAVY RAIN MAY ALSO FALL OVER A SHORT PERIOD OF TIME WHICH MAY LEAD TO FLOODING OR FLASH FLOODING. .DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY. THERE IS A CONTINUED CHANCE OF THUNDERSTORMS THURSDAY. SOME OF THESE THUNDERSTORMS MAY PRODUCE HEAVY RAIN. ISOLATED THUNDERSTORMS ARE ALSO POSSIBLE DURING THE DAY FRIDAY. .SPOTTER INFORMATION STATEMENT... SPOTTERS MAY BE NEEDED THIS AFTERNOON INTO THIS EVENING AND AGAIN OVERNIGHT INTO THURSDAY MORNING. && COMPLETE FORECAST INFORMATION IS AVAILABLE ON THE NWS CHICAGO WEBPAGE: WEATHER.GOV/CHICAGO LMZ740>745-201615- 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- 1108 AM CDT WED AUG 19 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 ARE POSSIBLE OVER SOUTHERN LAKE MICHIGAN THIS AFTERNOON AND THIS EVENING AND AGAIN OVERNIGHT. SOME OF THESE STORMS MAY PRODUCE WIND GUSTS TO 35 KNOTS. .DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY. THERE IS A CONTINUED CHANCE OF THUNDERSTORMS THURSDAY. ISOLATED THUNDERSTORMS ARE ALSO POSSIBLE DURING THE DAY FRIDAY. A SMALL CRAFT ADVISORY MAY BE NEED THURSDAY AND THURSDAY NIGHT FOR WINDS UP TO 25 KNOTS. && 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- 870-872-874-876-878-201615- 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- 1108 AM CDT WED AUG 19 2009 THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE OPEN WATERS OF LAKE MICHIGAN. .DAY ONE...TODAY AND TONIGHT. THUNDERSTORMS ARE LIKELY ACROSS THE ENTIRE LAKE FROM THIS AFTERNOON THROUGH THURSDAY MORNING. SOME OF THESE STORMS MAY PRODUCE WIND GUSTS TO 35 KNOTS. .DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY. THERE IS A CONTINUED CHANCE OF THUNDERSTORMS THURSDAY. ISOLATED THUNDERSTORMS ARE ALSO POSSIBLE DURING THE DAY FRIDAY. && COMPLETE FORECAST INFORMATION IS AVAILABLE ON THE NWS CHICAGO WEBPAGE: WEATHER.GOV/CHICAGO
The Chicago radar (KLOT), 90 km away, was scanning. The volume nearest the first event began at 21:03 UTC.
5 thunderstorm wind, 3 tornado, 1 flood, 1 hail. Local standard time, as filed.
A delivery truck and trailer were blown against a guard shack and destroyed just west of Interstate 39 in Oglesby. Another trailer was tipped over and the roof of thrid trailer was blown off.
Numerous trees, tree limbs and power lines were blown down across much of Streator. One tree fell onto a house on Washington Street. Wind gusts were estimated as high as 80 mph.
Damage was reported to a storage trailer and to the roof of a gas station near Interstate 55.
A mobile home was overturned just south of Lorenzo Road.
Yard and street flooding was reported north of Mendota with a storm total rainfall of 2.49 inches.
A tornado touched down just north of Route 38. At this location, a field of corn was flattened in a covergent manner towards the northwest. Damage was rated EF0 with winds near 65 mph and a path width of 20 yards. The tornado moved northwest and intensified as it moved along Route 47 where it snapped off and uprooted multiple large hardwood and softwood trees. The damage at this location was blown in a convergent pattern to the northwest. EF1 damage was observed with winds estimated near 105 mph and a path width of 40 yards. The tornado continued to the northwest maintaining its strength causing more tree damage along Route 47. Several trees were snapped off and consistently blown in the same direction to the northwest. Several cars were damaged by falling tree limbs. Damage was rated EF1 at this location with winds near 105 mph and a path width of 40 yards. Several residences along Route 47 continued to receive damage to many trees on their property even as the tornado was weakening. The last of the damage observed was in a corn field just to the west of Route 47. Here corn was flattened and twisted before the the tornado lifted with the damage rated EF0 with winds near 65 mph.
A tornado touched down along County Road 2100 East, north of the intersection of County Roads 2100 North and 2100 East. The initial touchdown was in a corn field where the corn was laid down in a convergent pattern. At this location, the tornado was approximately 20 yards wide. The tornado then crossed County Road 2100 North where it caused damage to trees and a small corn silo next to a farm house. Just behind this farm house, several large trees were broken near their base with one tree uprooted. Most of these trees were around three feet in diameter. Some internal rot was noted in a few of the trees making them more susceptible to wind damage. The tornado then appears to have lifted briefly before touching down again just behind a home along County Road 2200 East, between County Roads 2100 North and 2150 North. At this location, significant tree damage was observed with multiple limbs between one and two feet in diameter being broken and falling in a convergent manner. Also at this location, a detached garage was destroyed with debris being scattered 50 to 100 feet to the northeast. This appears to be the point along the damage path where the tornado reached its maximum intensity with an estimated peak wind speed of 105 mph and a width of 50 yards. The tornado then crossed County Road 2100 East causing damage to corn along both County Road 2100 East and County Road 2150 North. After crossing County Road 2150 North, the tornado destroyed a barn housing farming equipment, measuring 44 by 72 feet. Debris from this barn was scattered in all directions from the barn's original location. Several pieces of farm equipment estimated to weigh between 5,000 and 15,000 pounds were moved several feet north and northeast of their original location including a grain wagon which was lifted and placed on top of other farm equipment. After destroying the barn, the tornado moved northeast through a corn field where additional crop damage was observed. The tornado then again briefly lifted before striking a home and a detached garage along County Road 2340 East. Siding and minor roof and shingle damage was observed on the house and the detached garage lost its roof and suffered a collapse of the south wall. At this location, the tornado was estimated to be about 40 yards wide. The tornado appears to have lifted as it crossed County Road 2340 East.
A tornado touched down in a subdivision about a half mile north of Route 64. At this location, several large hardwood tree limbs were snapped and twisted off. Damage here was rated EF0 with winds near 75 mph and a path width of 30 yards. The tornado quickly moved to the northeast where it continued to cause damage to multiple large trees in this subdivision. The tornado began to weaken and produced the last of its damage about a quarter mile north of Route 64 where several large tree limbs were snapped off. Damage was rated EF0 with winds near 70 mph and a path width of 30 yards.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Illinois in 2009Every state in 2009This day in weather historyThe tornado archive for Illinois, 2009Warnings 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: 193882, 193846, 193847, 193854, 193853, 193848, 193850, 193852, 193851, 193849.