Strong upper level ridge built up over the region from July 25th through 29th. This ushered in much warmer air and higher dewpoints.
Every event with a place to put it; 17 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 LSX wrote it up.
Strong upper level ridge built up over the region from July 25th through 29th. This ushered in much warmer air and higher dewpoints. So heat index values 100+ were reported from July 25th through 29th. The hottest days were July 27th, 28th and 29th, so an excessive heat warning was issued for portions of northeast/east central Missouri and west central/southwest Illinois. At least 50 people were seen in hospital emergency room departments during this three day period in St. Louis County/City for heat-related illnesses.
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 St. Louis, MO wrote its last area forecast discussion before the first event at Jul 26, 5:24 PM CST, 15 hours 36 minutes earlier.
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</html>The national radar mosaic for the moment the first event began.
17 excessive heat. Local standard time, as filed.
Excessive heat across the county with highs between 100 to 103 degrees each day. Heat index values as high as 114 both days.
Excessive heat across the county with highs up to 100 degrees each day. Heat index values as high as 114 both days.
Excessive heat across the county with highs mid 90s to 101 degrees each day. Heat index values as high as 115 both days.
Excessive heat across the county with highs mid to upper 90s degrees each day. Heat index values as high as 107 both days.
Excessive heat across the county with highs mid to upper 90s degrees each day. Heat index values as high as 107 both days.
Excessive heat across the county with highs mid to upper 90s degrees each day. Heat index values as high as 107 both days.
Excessive heat across the county with highs mid to upper 90s degrees each day. Heat index values as high as 107 both days.
Excessive heat across the county with highs mid to upper 90s degrees each day. Heat index values as high as 107 each day.
Excessive heat across the county with highs mid to upper 90s degrees each day. Heat index values as high as 110 each day.
Excessive heat across the county with highs mid to upper 90s degrees each day. Heat index values as high as 110 each day.
Excessive heat across the county with highs 95 to 100 each day. Heat index values as high as 110 each day.
Excessive heat across the county with highs 95 to 100 each day. Heat index values as high as 110 each day.
Excessive heat across the county with highs 95 to 100 each day. Heat index values as high as 110 each day.
Excessive heat across the county with highs 95 to 100 each day. Heat index values as high as 110 each day.
Excessive heat across the county with highs 95 to 100 each day. Heat index values as high as 110 each day.
Excessive heat across the county with highs 95 to 100 each day. Heat index values as high as 110 each day.
Excessive heat across the county with highs mid to upper 90s degrees each day. Heat index values as high as 107 each day.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Illinois in 2023Every state in 2023This day in weather historyWarnings in Illinois, July 2023
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: 1141418, 1141419, 1141429, 1141436, 1141437, 1141438, 1141439, 1141449, 1141450, 1141451, 1141452, 1141453, 1141454, 1141455, 1141456, 1141457, 1141458.