A large ridge of high pressure in the central United States combined with high levels of humidity to produce excessive heat conditions in west central Illinois August 1st and all of central Illinois August 2nd. There were no reports of heat related fatalities during this relatively short heat episode.
Every event with a place to put it; 14 filed by county or forecast zone are drawn at its center, in a lighter ring. 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 ILX wrote it up.
A large ridge of high pressure in the central United States combined with high levels of humidity to produce excessive heat conditions in west central Illinois August 1st and all of central Illinois August 2nd. There were no reports of heat related fatalities during this relatively short heat episode.
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 Lincoln, IL wrote its last area forecast discussion before the first event at Aug 1, 2:00 PM CST, 30 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LINCOLN IL 300 PM CDT MON AUG 1 2011 .DISCUSSION... ISSUED 300 PM CDT MON AUG 1 2011 SHORT TERM...TONIGHT THROUGH THURSDAY... HEAT HEADLINES AND THUNDERSTORM CHANCES WITH THE NEXT FRONT WILL BE THE MAIN FORECAST ISSUES IN THE SHORT RANGE. FIRST...THE HEAT. TEMPERATURES OUT WEST ARE WELL ABOVE 100 OVER MANY AREAS OF CENTRAL/WESTERN MISSOURI AND WESTWARD FROM THERE. CURRENT OBJECTIVE ANALYSIS SUGGESTS 850MB TEMPERATURES ARE NOW 22-23 DEG C OVER THE CENTRAL IL...AND BOTH THE NAM AND GFS PREDICT 850MB TEMPS AROUND 26 DEG TUESDAY AFTERNOON. THIS WOULD PUT TEMPERATURES AT LEAST IN THE UPPER 90S...ALONG WITH DEWPOINTS IN THE MID 70S. POSSIBLY A FEW 100 DEGREE HIGHS IN THE SOUTHWEST. THIS YIELDS HEAT INDEX VALUES AROUND 110 FROM SPRINGFIELD TO PEORIA AND WESTWARD. SOME LOCATIONS OVER THE SOUTHWESTERN PORTIONS OF THE FORECAST AREA HAVE A GOOD SHOT AT SEEING NEAR 110 THIS AFTERNOON AS WELL. WILL THEREFORE UPGRADE THE HEAT ADVISORY IN THE SOUTHWEST TO A WARNING VALID FROM NOW UNTIL 7 PM TUE. ALTHOUGH THE IL RIVER VALLEY AREAS FURTHER NORTH WILL ALSO HAVE 110 HEAT INDICES ON TUE...THEY WILL NOT BE THAT WARM FOR MOST OF THE AREA THIS AFTERNOON. THUS ONLY ADVISORY CRITERIA APPLIES. CURRENT MCS OVER SOUTHEASTERN MN IS FORECAST TO MOVE SOUTHEAST BUT STAY NORTH OF THE FORECAST AREA TONIGHT. FURTHER UPSTREAM...WATER VAPOR SATELLITE LOOPS SHOW A VIGOROUS UPPER SHORTWAVE MOVING NORTHEAST THROUGH NORTHERN ROCKIES. THIS SYSTEM WILL PICK UP THE SURFACE LOW ALREADY OVER SOUTH DAKOTA AND PUSH IT EASTWARD ON TUESDAY...WITH THE ATTENDING COLD FRONT APPROACHING THE NORTHERN COUNTIES OF THE FORECAST AREA TOWARD 00Z WED. AIRMASS AHEAD OF THE FRONT WILL BE HOT AND CAPPED...WITH MAIN CHANCES OF STORMS TO THE NORTH OF THE FRONT WHERE PARCELS CAN GET MECHANICALLY LIFTED TO THE LFC. HAVE HELD ONTO SLIGHT CHANCE POPS IN THE EXTREME NORTH FOR TUESDAY AFTERNOON...BUT BETTER CHANCES WILL HOLD OFF UNTIL TUESDAY NIGHT. ONCE THE FRONT CONTINUES SOUTHWARD INTO MORE OF THE AREA TUESDAY EVENING...LOOKS LIKE A BETTER-THAN-EVEN SHOT AS STORMS NORTH OF AN EAST-WEST LINE THROUGH BLOOMINGTON BEFORE PRECIPITATION COVERAGE DECREASES AGAIN AFTER MIDNIGHT. WILL THEREFORE HAVE LIKELY POPS UP THERE TUE EVENING...WITH CHANCE POPS FURTHER SOUTH. AREAS ALONG AND SOUTH OF I-70 WILL ONLY HAVE A SLIGHT CHANCE AFTER MIDNIGHT. ALTHOUGH THE MODELS SHOVE THE FRONT WELL SOUTH OF THE FORECAST AREA BY NOON WEDNESDAY...WILL RETAIN CHANCE POPS IN THE SOUTHEAST THROUGH THE AFTERNOON IN CASE THE FRONT GETS HUNG UP AS THE UPPER SUPPORT PULLS AWAY THROUGH THE GREAT LAKES. WEDNESDAY NIGHT AND THURSDAY LOOK PRETTY MUCH DRY AND NOT AS WARM AS HIGH PRESSURE MOVES INTO THE MIDWEST. THE PREVIOUS GFS WAS TRYING TO PUSH THE NEXT ROUND OF PRECIPITATION INTO WESTERN IL AS EARLY AS LATE WEDNESDAY OR THURSDAY...BUT BELIEVE THAT THIS WAS DUE TO EXCESSIVE GRID-SCALE FEEDBACK. THE LATEST GFS AS WELL AS THE NAM AND ECMWF KEEPS THE HIGH PRESSURE IN CONTROL UNTIL AT LEAST THURSDAY NIGHT. SO WILL HAVE POPS BELOW SLIGHT CHANCE UNTIL THE NEXT SYSTEM GETS CLOSER ON FRIDAY. LONG TERM...FRIDAY THROUGH MONDAY... UPPER PATTERN BEGINNING FRIDAY WILL CONTINUE WITH THE BROAD UPPER RIDGE THAT WILL EXTEND WEST-EAST ACROSS THE CENTRAL AND SOUTHERN CONUS. AN UPPER SHORTWAVE WILL MOVE ALONG THE NORTHERN PERIPHERY OF THE RIDGE AND BRING A COLD FRONT THROUGH THE MIDWEST ON FRIDAY. THIS IS SIMILAR TO PREVIOUS RUNS...SO WILL CONTINUE THE POPS FOR THAT TIMEFRAME AND CONTINUE A MENTIONABLE POP FOR THE EAST FRIDAY NIGHT. THE MODELS ARE STILL DIFFERING SOMEWHAT ON HOW FAR SOUTH THE FRONT WILL PENETRATE INTO THE UPPER RIDGE ON SATURDAY...SO WILL CONTINUE WITH SLIGHT CHANCE POPS THEN. AFTER A BREAK ON SUNDAY...THE MODELS HAVE DIFFERENT TIMING ON THE NEXT SYSTEM FOR EARLY NEXT WEEK. THE ECMWF BRINGS A FRONT THROUGH...WHILE THE GFS HANGS ON TO THE SURFACE RIDGE LONGER. FORECAST CONFIDENCE BECOMES LOW FOR DAYS 6 AND 7 AS THE POTENTIAL RAIN-MAKER WILL BE SMALL SCALE AND DIFFICULT TO RESOLVE THAT FAR AHEAD OF TIME. WILL KEEP POPS OUT OF THE GRIDS FOR NOW UNTIL THE SITUATION BECOMES BETTER DEFINES. 04 && .AVIATION... ISSUED 1241 PM CDT MON AUG 1 2011 SCT TO OCCASIONALLY BKN CU FIELD WITH BASES AROUND 3500FT WILL BE NOTED ACROSS CENTRAL ILLINOIS TODAY. THESE CLOUDS WILL QUICKLY FADE AWAY TOWARD SUNSET...RESULTING IN CLEAR SKIES TONIGHT INTO TUESDAY MORNING. WINDS WILL INITIALLY BE LIGHT/VARIABLE THIS AFTN...THEN WILL BEGIN TO DEVELOP A LIGHT SOUTHERLY COMPONENT TONIGHT AS HIGH PRESSURE DRIFTS EAST OF THE REGION. WITH CLEAR SKIES AND LIGHT WINDS IN PLACE...PATCHY FOG WILL ONCE AGAIN DEVELOP LATE TNGT...ESPECIALLY ACROSS EAST-CENTRAL ILLINOIS WHERE WINDS WILL BE LIGHTEST. HAVE INCLUDED RESTRICTED VISBYS DOWN TO AROUND 4SM AT MOST SITES OVERNIGHT...BUT HAVE GONE SLIGHTLY LOWER TO 2SM FURTHER EAST AT KCMI. AS THE HIGH MOVES FURTHER AWAY AND A WEAK COLD FRONT APPROACHES FROM THE NORTHWEST...SOUTHWESTERLY WINDS WILL INCREASE INTO THE 10 TO 15KT RANGE AFTER 14Z. BARNES && .ILX WATCHES/WARNINGS/ADVISORIES... EXCESSIVE HEAT WARNING UNTIL 7 PM CDT TUESDAY FOR ILZ040-047>051. HEAT ADVISORY UNTIL 7 PM CDT TUESDAY FOR ILZ027>031-036>038- 041>046-052>057-061>063-066>068-071>073. &&
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE LINCOLN IL 327 PM CDT MON AUG 1 2011 ILZ027>031-036>038-041>046-053-055-057-021100- CHAMPAIGN-DE WITT-DOUGLAS-EDGAR-FULTON-KNOX-LOGAN-MACON-MARSHALL- MASON-MCLEAN-PEORIA-PIATT-STARK-TAZEWELL-VERMILION-WOODFORD- 327 PM CDT MON AUG 1 2011 ...HEAT ADVISORY IN EFFECT UNTIL 7 PM CDT TUESDAY... THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL ILLINOIS AND EAST CENTRAL ILLINOIS. .DAY ONE...TONIGHT HEAT INDEX READINGS WILL RANGE FROM 100 TO 105 DEGREES THROUGH EARLY EVENING. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY OPPRESSIVE HEAT AND HUMIDITY WILL PERSIST ON TUESDAY...AS AFTERNOON HIGH TEMPERATURES CLIMB INTO THE MIDDLE TO UPPER 90S. CORRESPONDING HEAT INDEX VALUES WILL REACH THE 105 TO 110 DEGREE RANGE. A WEAK COLD FRONT WILL TRIGGER SCATTERED THUNDERSTORMS ACROSS THE AREA TUESDAY NIGHT. WIDESPREAD SEVERE WEATHER IS NOT ANTICIPATED...HOWEVER A FEW OF THE STORMS ALONG AND NORTH OF THE I-74 CORRIDOR COULD PRODUCE GUSTY WINDS...FREQUENT LIGHTNING...AND LOCALLY HEAVY RAINFALL. ANOTHER APPROACHING FRONTAL BOUNDARY WILL BRING THUNDERSTORM CHANCES BACK INTO CENTRAL ILLINOIS THURSDAY NIGHT INTO FRIDAY. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT ANTICIPATED THROUGH TONIGHT. ILZ040-047>051-021100- CASS-MENARD-MORGAN-SANGAMON-SCHUYLER-SCOTT- 327 PM CDT MON AUG 1 2011 ...EXCESSIVE HEAT WARNING IN EFFECT UNTIL 7 PM CDT TUESDAY... THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL ILLINOIS. .DAY ONE...TONIGHT HEAT INDEX VALUES WILL RANGE FROM 100 TO 105 DEGREES THROUGH EARLY EVENING. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY OPPRESSIVE HEAT AND HUMIDITY WILL PERSIST ON TUESDAY...AS AFTERNOON HIGH TEMPERATURES CLIMB INTO THE MIDDLE TO UPPER 90S. CORRESPONDING HEAT INDEX VALUES WILL REACH THE 107 TO 112 DEGREE RANGE. A WEAK COLD FRONT WILL TRIGGER SCATTERED THUNDERSTORMS ACROSS THE AREA TUESDAY NIGHT. SEVERE WEATHER IS NOT ANTICIPATED. ANOTHER APPROACHING FRONTAL BOUNDARY WILL BRING THUNDERSTORM CHANCES BACK INTO CENTRAL ILLINOIS THURSDAY NIGHT INTO FRIDAY. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT ANTICIPATED THROUGH TONIGHT. ILZ052-054-056-061>063-066>068-071>073-021100- CHRISTIAN-CLARK-CLAY-COLES-CRAWFORD-CUMBERLAND-EFFINGHAM-JASPER- LAWRENCE-MOULTRIE-RICHLAND-SHELBY- 327 PM CDT MON AUG 1 2011 ...HEAT ADVISORY IN EFFECT UNTIL 7 PM CDT TUESDAY... THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL ILLINOIS...EAST CENTRAL ILLINOIS AND SOUTHEAST ILLINOIS. .DAY ONE...TONIGHT HEAT INDEX VALUES WILL RANGE FROM 100 TO 105 DEGREES THROUGH EARLY EVENING. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY OPPRESSIVE HEAT AND HUMIDITY WILL PERSIST ON TUESDAY...AS AFTERNOON HIGH TEMPERATURES CLIMB INTO THE MIDDLE TO UPPER 90S. CORRESPONDING HEAT INDEX VALUES WILL REACH THE 105 TO 110 DEGREE RANGE. A WEAK COLD FRONT WILL TRIGGER SCATTERED THUNDERSTORMS ACROSS THE AREA ON WEDNESDAY. SEVERE WEATHER IS NOT ANTICIPATED. ANOTHER APPROACHING FRONTAL BOUNDARY WILL BRING THUNDERSTORM CHANCES BACK INTO CENTRAL ILLINOIS THURSDAY NIGHT INTO FRIDAY. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT ANTICIPATED THROUGH TONIGHT. BARNES
The national radar mosaic for the moment the first event began.
14 excessive heat. Local standard time, as filed.
Temperatures in the middle 90s combined with dew point temperatures in the middle 70s to produce heat index values ranging from 110 to 115 degrees during the afternoon and early evening hours of August 1st and 2nd.
Temperatures in the middle 90s combined with dew point temperatures in the middle 70s to produce heat index values ranging from 110 to 115 degrees during the afternoon and early evening hours of August 1st and 2nd.
Temperatures in the middle 90s combined with dew point temperatures in the middle 70s to produce heat index values ranging from 110 to 115 degrees during the afternoon and early evening hours of August 1st and 2nd.
Temperatures in the middle 90s combined with dew point temperatures in the middle 70s to produce heat index values ranging from 110 to 115 degrees during the afternoon and early evening hours of August 1st and 2nd.
Temperatures in the middle 90s combined with dew point temperatures in the middle 70s to produce heat index values ranging from 110 to 115 degrees during the afternoon and early evening hours of August 1st and 2nd.
Temperatures in the middle 90s combined with dew point temperatures in the middle 70s to produce heat index values ranging from 110 to 115 degrees during the afternoon and early evening hours of August 1st and 2nd.
Temperatures in the middle 90s combined with dew point temperatures in the middle 70s to produce heat index values ranging from 105 to 110 degrees during the afternoon and early evening hours of August 2nd.
Temperatures in the middle 90s combined with dew point temperatures in the middle 70s to produce heat index values ranging from 105 to 110 degrees during the afternoon and early evening hours of August 2nd.
Temperatures in the middle 90s combined with dew point temperatures in the middle 70s to produce heat index values ranging from 105 to 110 degrees during the afternoon and early evening hours of August 2nd.
Temperatures in the middle 90s combined with dew point temperatures in the middle 70s to produce heat index values ranging from 105 to 110 degrees during the afternoon and early evening hours of August 2nd.
Temperatures in the middle 90s combined with dew point temperatures in the middle 70s to produce heat index values ranging from 105 to 110 degrees during the afternoon and early evening hours of August 2nd.
Temperatures in the middle 90s combined with dew point temperatures in the middle 70s to produce heat index values ranging from 105 to 110 degrees during the afternoon and early evening hours of August 2nd.
Temperatures in the middle 90s combined with dew point temperatures in the middle 70s to produce heat index values ranging from 105 to 110 degrees during the afternoon and early evening hours of August 2nd.
Temperatures in the middle 90s combined with dew point temperatures in the middle 70s to produce heat index values ranging from 105 to 110 degrees during the afternoon and early evening hours of August 2nd.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Illinois in 2011Every state in 2011This day in weather historyWarnings in Illinois, August 2011
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: 344506, 344507, 344508, 344510, 344511, 344512, 344518, 344525, 344530, 344535, 344536, 344537, 344538, 344539.