Extreme Heat Warnings Covered Iowa, Illinois, Missouri, Kentucky and Indiana Through the Weekend of Sept. 5

Update, Sept. 7, 2026: these warnings have expired. The last of them ran through Saturday night, Sept. 5; no Extreme Heat Warning from this event remains in effect. What follows describes the alerts as they stood on Thursday, Sept. 3. Anyone checking current conditions should use the National Weather Service’s active-alerts page rather than this page.

Dangerously hot conditions had put parts of five Midwest and Ohio Valley states under Extreme Heat Warnings that week, with heat index values the National Weather Service quotes as high as 110 degrees. As of about 10:11 a.m. CDT (15:11 UTC) Thursday, the National Weather Service’s active-alerts feed listed seven separate warnings, issued by five regional forecast offices, covering counties in Iowa, Illinois, Missouri, Kentucky and Indiana. The count moves through the day as alerts expire and new ones are issued. The warnings’ end times run from this evening through Saturday night.

Key facts

Seven Extreme Heat Warnings were active as of about 10:11 a.m. CDT (15:11 UTC) Thursday, Sept. 3, issued by five NWS offices covering counties in Iowa, Illinois, Missouri, Kentucky and Indiana.
That count is a snapshot and can change within hours — alerts on the NWS active-alerts feed expire and new ones are issued through the day.
Heat index values quoted in the warnings (verbatim, by office): NWS Chicago “100 to 105”; NWS Quad Cities “100 to 110”; NWS Lincoln IL “up to 105” (both its warnings); NWS Paducah “105 to 110”; NWS St. Louis “up to 110” and “up to 107” (its two warnings).
Earliest warning headline end time: NWS Chicago’s, at 7 p.m. CDT today, Thursday, Sept. 3.
Latest warning headline end times: NWS Paducah’s and both of NWS St. Louis’s, at 8 p.m. CDT Saturday, Sept. 5.
13 Heat Advisories were also active in the same window — in Kansas, most of Indiana, parts of Ohio and eastern Kentucky, West Virginia, Virginia, North Carolina, Maryland, Washington, D.C., and ten counties in northwest Georgia — plus a separate advisory for Puerto Rico and the U.S. Virgin Islands.
No area of the country was under an Extreme Heat Watch at that same observation time.

Where the warnings apply, and when they end

Chicago (Cook County), Illinois — Cook County’s warning has the earliest headline end time: NWS Chicago issued it at 1:08 a.m. CDT, and the alert headline says it runs until 7 p.m. CDT this evening, Thursday, Sept. 3. It quotes “heat index values of 100 to 105,” and the office notes this is “the third day in a row with a forecast or observed maximum heat index over 100 degrees” — adding that a cold front, possibly with thunderstorms, should move through afterward and bring relief.
Quad Cities area, Iowa/Illinois/Missouri — West of Chicago, NWS Quad Cities’ warning covers counties in eastern Iowa, northwestern Illinois and northeastern Missouri, quoting “heat index values of 100 to 110,” and the alert headline says it is in effect until 7 p.m. CDT Friday, Sept. 4.
Central Illinois — NWS Lincoln IL has two warnings running at once, both quoting heat index values “up to 105”: the alert headline for one, covering central Illinois counties, says it runs until 7 p.m. CDT Friday, Sept. 4, and the headline for the other, covering south-central Illinois counties, says it runs until 7 p.m. CDT Saturday, Sept. 5.
Western Kentucky, southern Illinois, southwest Indiana, southeast Missouri — NWS Paducah’s warning quotes “heat index values 105 to 110” and runs until 8 p.m. CDT Saturday, Sept. 5; the office adds that “overnight low temperatures in the mid 70s will provide little relief from the heat.”
St. Louis area, Missouri and Illinois — NWS St. Louis has two warnings covering an even wider stretch of territory. The first, for the city of St. Louis, St. Louis County, St. Charles and Jefferson counties in Missouri and Madison, St. Clair and Monroe counties in Illinois, quotes “heat index values up to 110.” A separate, larger warning from the same office — covering roughly 39 more Missouri counties across the central and southeastern parts of the state, plus additional Illinois counties — quotes “heat index values up to 107.” Both alert headlines say they run until 8 p.m. CDT Saturday, Sept. 5.

Advisories beyond the warning zone

Beyond the five states under Warnings, a wider tier of alerts extends across the country. A Heat Advisory is one step down — still hot enough to be dangerous, just below Warning-level extremes — and NWS had 13 of those active in the same window, stretching well beyond the warning zone: in Kansas; across most of Indiana; in parts of Ohio and eastern Kentucky; in West Virginia, Virginia and North Carolina; in Maryland and Washington, D.C.; and in ten counties in northwest Georgia. Heat index figures in those advisories run from about 100 up to 108, depending on the office. Indiana and Kentucky each show up under both levels — a Warning covering part of the state, an Advisory covering other counties — because a single state can be split between the two levels; that is not a contradiction. NWS San Juan has also issued a separate Heat Advisory for Puerto Rico and the U.S. Virgin Islands — a distinct product, which no source ties to the same weather system driving the Midwest warnings. No area of the country was under an Extreme Heat Watch at the same observation time. NWS’s national homepage points to what is behind the pattern: a banner there reads “Threats of Heavy Rainfall, Severe Thunderstorms and Dangerous Heat,” with the note that “In-between these systems, a dome of high pressure and heat for central and eastern states.”

What officials are telling residents to do

Every office’s warning boils down to the same advice: drink enough water, stay somewhere air-conditioned, keep out of direct sun, and save any hard physical work for early morning or evening. Check on relatives and neighbors, never leave a child or a pet in a parked car, and learn to recognize heat exhaustion and heat stroke — heat stroke is a 911 call. The St. Louis warning adds one more piece of guidance, from the Occupational Safety and Health Administration, for people working outdoors: “frequent rest breaks in shaded or air conditioned environments.”

Where to call

NWS Chicago: call 311 for a well-being check or cooling-center information.
NWS St. Louis: the United Way of Greater Saint Louis (800-427-4626, or 2-1-1 from a landline) for cooling centers and energy assistance, and Cool Down Saint Louis (314-241-7668).

No other office’s alert named an open cooling center, and no state or city government has announced a school closure tied to this heat. No death or hospitalization has been officially linked to this event.

What happens next

NOAA (National Oceanic and Atmospheric Administration)’s Climate Prediction Center had already flagged the pattern before the warnings went up, posting a “Long-Duration Heat Wave” key message on its homepage dated Sept. 1 — two days ahead of Thursday’s warnings — a sign forecasters were tracking this as a multi-day event rather than a single hot afternoon.

The earliest relief comes to Chicago this evening; some warnings in Illinois, Missouri and Kentucky extend through Saturday night.