During the evening of July 20th, an isolated supercell developed over northern Illinois producing baseball size hail and damaging winds.
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.
During the evening of July 20th, an isolated supercell developed over northern Illinois producing baseball size hail and damaging winds.
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 Jul 20, 5:51 PM CST, 49 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL 651 PM CDT SAT JUL 20 2013 .DISCUSSION... 312 PM CDT THE MAIN FORECAST CONCERNS DURING THE FORECAST PERIOD WILL BE TEMPERATURES AS WELL AS THE THREATS OF CONVECTION LATE SUNDAY INTO MONDAY AND AGAIN ON TUESDAY. THE PRIMARY COLD FRONTAL BOUNDARY HAS PUSHED WELL SOUTH OF THE AREA THIS AFTERNOON...AND THIS HAS BEEN THE FOCUS FOR CONVECTIVE ACTIVITY ACROSS PORTIONS OF EAST CENTRAL ILLINOIS THROUGH THE MORNING. HOWEVER...A SECONDARY COLD FRONT IS CURRENTLY MOVING ACROSS FAR SOUTHERN WISCONSIN AND THIS APPEARS TO BE SPARKING OFF A FEW SHOWERS ACROSS FAR NORTHERN ILLINOIS EARLY THIS AFTERNOON. THE CU FIELD HAS BECOME INCREASING AGITATED AHEAD OF THIS BOUNDARY UP NEAR KRFD...SO I IT APPEARS THAT SOME ADDITIONAL ISOLATED SHOWERS OR THUNDERSTORMS WILL DEVELOP WITHIN THE NEXT HOUR OR TWO. DEW POINTS NEAR 60 IS LIMITING THE OVERALL INSTABILITY...THEREFORE WE ARE NOT EXPECTING MUCH MORE THAN A FEW SHOWERS...WITH POSSIBLY CONTAIN A FEW LIGHTNING STRIKES. I ADDED SOME ISOLATED SHOWERS TO THE FORECAST THROUGH EARLY THIS EVENING TO ACCOUNT FOR THIS ACTIVITY. OTHERWISE...THIS FRONT WILL NOT HAVE MUCH OF AN AFFECT...AS THE COLDER AIR SHIFTS EAST ACROSS THE UPPER GREAT LAKES. ON SUNDAY...I CHOSE TO WARM TEMPERATURES A COUPLE OF DEGREES AS IT APPEARS NOT MUCH COOLER AIR WILL FILTER IN ACROSS THE AREA. CONSIDERING 925 MB TEMPERATURES ARE PROGGED TO BE SIMILAR TODAY...I THINK WE WILL ONCE AGAIN WARM INTO THE LOW TO MID 80S...EXCEPT RIGHT ALONG THE LAKE...WHERE AN ONSHORE FLOW SHOULD LIMIT THE WARMTH. I DID NOT GO AS WARM AS TODAY...HOWEVER...AS IT APPEARS THERE WILL BE MORE CLOUDS AROUND DURING THE DAY. THE OTHER STORY FOR SUNDAY...WILL BE THE INCREASING THREAT FOR CONVECTIVE ACTIVITY...ESPECIALLY SUNDAY NIGHT. AN UPPER LEVEL DISTURBANCE...NOW ACROSS THE PACIFIC NORTHWEST...IS PROGGED TO SHIFT EAST-SOUTHEASTWARD ACROSS IOWA SUNDAY AFTERNOON AND THEN ACROSS NORTHERN ILLINOIS SUNDAY NIGHT. THIS WILL LIKELY BE THE DRIVER OF THUNDERSTORMS ACROSS MUCH OF THE AREA INTO EARLY MONDAY. IT CURRENTLY APPEARS CHANCES FOR SOME STORMS MAY INCREASE INCREASE ACROSS MY WESTERN COUNTIES AS EARLY AS TOMORROW AFTERNOON AS THERE SHOULD BE LITTLE TO NO CAP IN PLACE. HOWEVER...IT APPEARS THE BETTER CHANCES WILL BE SUNDAY NIGHT AS THE UPPER LEVEL DISTURBANCES MOVES ACROSS THE AREA. THERE HAS BEEN...AND CONTINUES TO BE DISAGREEMENTS ON THE ACTUAL STRENGTH OF THIS WAVE...AND HENCE THE OVERALL AMOUNTS OF RAIN THAT MAY FALL. IN PARTICULAR...THE 12 UTC GEM IS FORECASTING A MUCH STRONGER SYSTEM WILL A STRONGER LOW LEVEL JET/MOISTURE TRANSPORT...AND HENCE IT SUGGESTS A VERY HEAVY RAINFALL EVENT SUNDAY NIGHT FOR NORTHERN ILLINOIS. THIS DOES APPEAR TO BE OVERDONE...WITH MOST OTHER GUIDANCE INDICATING A WEAKER LOWER LEVEL JET. IN SPITE OF THIS...SOME DECENT RAINFALL IS STILL POSSIBLE ACROSS PORTIONS OF THE AREA WITH THIS MCS ACTIVITY SUNDAY NIGHT...WITH PWATS EXPECTED TO BACK UP IN THE 1.6 YO 1.7 INCH RANGE AS THE SURFACE FRONTAL ZONE TO THE SOUTH LIFTS BACK NORTHWARD ALLOWING SOME OF THE MOISTURE RICH AIR TO MAKE A COMEBACK. I DID TREND THE HIGHEST POPS ACROSS THE SOUTHERN CWA...CLOSER TO THE FORECASTED TRACK OF THE DISTURBANCE. MONDAY APPEARS TO BE ANOTHER FAIRLY WARM DAY ACROSS THE REGION. SOME OF THE CONVECTIVE ACTIVITY MAY LINGER ACROSS MY SOUTHEASTERN COUNTIES MONDAY MORNING...OTHERWISE IT APPEARS ASIDE FROM A THE POSSIBILITY FROM SOME ISOLATED TO WIDELY SCATTERED DEVELOPMENT IN THE AFTERNOON...POSSIBLY FOCUSED ON A LAKE BREEZE...IT APPEARS MOST AREAS MAY REMAIN DRY IN THE AFTERNOON. WITH 925 MB TEMPERATURES PROGGED TO BE BACK AROUND 24 DEGREES CELSIUS...THIS COULD RESULT IN TEMPERATURES NEAR 90 DEGREES AND POSSIBLE HEAT INDEX VALUES BACK TO INTO THE MID 90S. THE ACTIVE WEATHER PATTERN WILL CONTINUE...WITH A COLD FRONT APPROACHING AND MOVING ACROSS THE AREA ON TUESDAY. THIS LOOKS TO INTERACT WITH THIS WARM MOIST AIR MASS...TO RESULT IN MORE THUNDERSTORMS FOR TUESDAY. IN THE WAKE OF THIS FRONT...MUCH COOLER AND DRIER AIR WILL FILTER IN ACROSS THE AREA AS A SURFACE RIDGE OF HIGH PRESSURE BUILDS IN ACROSS THE WESTERN GREAT LAKES. THIS SHOULD RESULT IN A COUPLE OF QUIET AND NICE DAYS ACROSS THE AREA THROUGH THURSDAY. BY THE END OF THE WEEK...ANOTHER SYSTEM COULD AFFECT THE AREA WITH MORE RAIN. HOWEVER...THERE IS GOOD AGREEMENT THAT ANOTHER...POTENTIALLY STRONGER SHOT OF COOLER AIR WILL SPILL ACROSS THE AREA BY NEXT WEEKEND. THIS COULD RESULT IN HIGHS IN THE 70S. KJB && .AVIATION... //ORD AND MDW CONCERNS...UPDATED 00Z... * THUNDERSTORM CHANCES MAINLY IN THE LATE AFTERNOON AND EVENING. BMD //DISCUSSION...UPDATED 00Z... SHOULD BE A FAIRLY QUIET NIGHT ACROSS NORTHERN ILLINOIS. A FEW SHOWERS TO THE NORTH OF THE AREA SHOULD DIMINISH WITH SUNSET THIS EVENING. A STRONG LAKE BREEZE HAS PUSHED ACROSS THE CHICAGO TERMINALS LEAVING THEM UNDER EASTERLY FLOW. THE BOUNDARY SHOULD PUSH ACROSS RFD AROUND 02Z SWITCHING THEIR WINDS AROUND TO THE EAST AS WELL. VFR CONDITIONS AND LIGHT EAST/NORTHEAST WINDS WILL PREVAIL THE REMAINDER OF THE NIGHT. MOS GUIDANCE IS HINTING AT THE POTENTIAL FOR SOME FOG/BR AT DPA/RFD BUT WILL HOLD OFF ANY MENTION TO SEE HOW WEAK THE WINDS BECOME AND IF SKIES CLEAR...WHICH AT THE MOMENT ARE EXPECTED TO BE PROHIBITIVE FACTORS. HIGH PRESSURE SETTLING OVER LAKE MICHIGAN SUNDAY SHOULD HELP KEEP WINDS OFF THE LAKE FOR THE CHICAGO TERMINALS...BUT RFD IS EXPECTED TO BEGIN TO SEE RETURN FLOW EARLIER IN THE DAY AS A WARM FRONT LIFTS BACK TO THE NORTH. INSTABILITY GROWS AWAY FROM THE INFLUENCE OF THE LAKE AND CANNOT RULE OUT SCATTERED CONVECTION DEVELOPING IN THE AFTERNOON...MAINLY IMPACTING RFD. EXPECT THE WARM FRONT TO LIFT ACROSS THE CHICAGO TERMINALS LATE IN THE EVENING ALLOWING WINDS TO BEGIN TO TURN SOUTHEASTERLY. BMD //ORD AND MDW CONFIDENCE...UPDATED 00Z... * HIGH CONFIDENCE IN ALL FORECAST ELEMENTS. BMD //OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z... MONDAY...CHC TSRA. TUESDAY...CHC TSRA. WEDNESDAY...VFR. THURSDAY...VFR. FRIDAY...CHC TSRA. BMD && .MARINE... 312 PM CDT THE PUSH OF COOL AIR BEHIND THE SECONDARY FRONT WAS LESS IMPRESSIVE THAN EXPECTED...SO WINDS IN THE NEAR SHORE WILL LIKELY ONLY TOP OUT AT AROUND 20 KT AND LIMITED DURATION OF STRONGER NORTHEAST FETCH WILL KEEP WAVES BELOW SMALL CRAFT CRITERIA AT ABOUT 3 TO 5 FT FOR THE ILLINOIS ZONES AND A BIT SMALLER FOR THE INDIANA ZONES. THUS HAVE CANCELED SMALL CRAFT ADVISORY THAT WAS SET TO TAKE EFFECT AT 4PM THIS AFTERNOON. HIGH PRESSURE WILL CONTINUE TO SPREAD IN FROM THE NORTHWEST SO INITIALLY BRISK EAST- NORTHEAST WINDS FOR THE SOUTH/CENTRAL PORTION OF THE LAKE WILL DIMINISH. AS THE HIGH PUSHES EAST SUNDAY NIGHT INTO MONDAY...WINDS WILL TURN SOUTHERLY AND INCREASE AS STRONG LOW PRESSURE TRACKS NEAR OR NORTH OF LAKE SUPERIOR. THEN AS THIS LOW MOVES NORTHEAST INTO QUEBEC BY EARLY TUESDAY...IT WILL DRAG A COLD FRONT SOUTH DOWN THE LAKE. GUIDANCE IS IN GOOD AGREEMENT IN A PERIOD OF STRONG NORTHERLY WINDS SURGING DOWN THE LAKE BEHIND THIS FRONT SO HAVE CONTINUED TREND FROM PREVIOUS ISSUANCE AND BUMPED SPEEDS UP WITH GUSTS TO 30 KT DUE TO UNSTABLE CONDITIONS IN COOL AIRMASS. WINDS WILL THEN DIMINISH BY WEDNESDAY AND REMAIN LIGHT INTO LATE NEXT WEEK WITH HIGH PRESSURE OVER THE REGION. RC && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...NONE. && VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE) FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT: WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV WWW.TWITTER.COM/NWSCHICAGO WWW.YOUTUBE.COM/NWSCHICAGO
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL 341 PM CDT SAT JUL 20 2013 ILZ003>006-008-010>014-019>023-032-033-039-INZ001-002-010-011-019- 212045- 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- 341 PM CDT SAT JUL 20 2013 /441 PM EDT SAT JUL 20 2013/ THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH CENTRAL ILLINOIS... NORTHEAST ILLINOIS AND NORTHWEST INDIANA. .DAY ONE...TONIGHT. THERE IS A SMALL CHANCE OF AN ISOLATED THUNDERSHOWER EARLY THIS EVENING ACROSS FAR NORTHERN ILLINOIS...NORTH OF INTERSTATE 88. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY. THERE IS A GOOD CHANCE OF THUNDERSTORMS SUNDAY AFTERNOON THROUGH MONDAY MORNING AND AGAIN MONDAY NIGHT THROUGH TUESDAY. HEAVY RAINFALL MAY ACCOMPANY THESE STORMS. THERE WILL BE ANOTHER CHANCE OF THUNDERSTORMS AGAIN ON FRIDAY AND SATURDAY. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NECESSARY THROUGH TONIGHT. && LMZ740>745-212045- 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- 341 PM CDT SAT JUL 20 2013 THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE ILLINOIS NEARSHORE WATERS OF LAKE MICHIGAN AND THE INDIANA NEARSHORE WATERS OF LAKE MICHIGAN. .DAY ONE...TONIGHT. NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY. WINDS AND WAVES HAZARDOUS TO SMALL CRAFT ARE EXPECTED TUESDAY AFTERNOON THROUGH WEDNESDAY AFTERNOON. THERE IS A CHANCE OF THUNDERSTORMS SUNDAY NIGHT THROUGH MONDAY MORNING AND AGAIN TUESDAY. ADDITIONAL THUNDERSTORMS ARE ALSO POSSIBLE FRIDAY AND SATURDAY. && LMZ080-261-362-364-366-563-565-567-669-671-673-675-777-779-868- 870-872-874-876-878-212045- 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 TWO 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- 341 PM CDT SAT JUL 20 2013 THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE OPEN WATERS OF LAKE MICHIGAN. .DAY ONE...TONIGHT. NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY. THERE WILL BE PERIODIC THUNDERSTORM CHANCES SUNDAY NIGHT THROUGH TUESDAY. ADDITIONAL THUNDERSTORMS ARE ALSO POSSIBLE FRIDAY AND SATURDAY...ESPECIALLY ACROSS SOUTHERN LAKE MICHIGAN. && KJB VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE) FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT: WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV WWW.TWITTER.COM/NWSCHICAGO WWW.YOUTUBE.COM/NWSCHICAGO
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL 730 PM CDT SAT JUL 20 2013 ILZ005-006-011-012-014-210115- COOK IL-DE KALB IL-KANE IL-LAKE IL-MCHENRY IL- 730 PM CDT SAT JUL 20 2013 ...SPECIAL WEATHER STATEMENT... AT 729 PM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A STRONG THUNDERSTORM NEAR MARENGO...MOVING SOUTHEAST AT 20 MPH. UP TO PENNY SIZE HAIL...WINDS TO 50 MPH...AND HEAVY DOWNPOURS ARE POSSIBLE WITH THIS STORM. CITIES AND TOWNS AFFECTED... MARENGO... LAKEWOOD... HUNTLEY... HAMPSHIRE... LAKE IN THE HILLS... ALGONQUIN... GILBERTS... SLEEPY HOLLOW... CARPENTERSVILLE... OTHER LOCATIONS AFFECTED... MCHENRY COUNTY COLLEGE... PRECAUTIONARY/PREPAREDNESS ACTIONS... GUSTY WINDS MAY CAUSE SMALL BRANCHES TO BE BLOWN DOWN...AND LOOSE OBJECTS TO BLOW AROUND. HEAVY RAINFALL COULD LEAD TO STANDING WATER ON ROADWAYS AND POOR VISIBILITY. SEEK SHELTER IN A STURDY STRUCTURE UNTIL THIS STORM HAS PASSED. && LAT...LON 4219 8812 4198 8853 4228 8870 4235 8855 TIME...MOT...LOC 0030Z 323DEG 19KT 4222 8855 BMD
The Chicago radar (KLOT), 77 km away, was scanning. The volume nearest the first event began at 00:40 UTC.
8 thunderstorm wind, 2 hail. Local standard time, as filed.
Severe winds uprooted 42 trees at Marengo Ridge Golf Course, some of which were from 1963 when the golf course opened.
Several trees were blown down in Huntley.
A construction trailer was blown over on Rockport Road. One person was injured.
A two-foot diameter tree was blown down on Highway 20. Other trees were blown down blocking the west bound lane.
Winds measured to 60 mph knocked out power near the intersection of Randall Road and Bowes Road. Large tree limbs were blown down in north Elgin.
Winds were estimated to 60 mph in St Charles.
Winds were estimated to 60 mph in Batavia.
A tree was blown down blocking westbound lanes of Aurora Avenue near Route 34.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Illinois in 2013Every state in 2013This day in weather historyWarnings in Illinois, July 2013
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: 468939, 468899, 468908, 468901, 468902, 468903, 468904, 468905, 468906, 468907.