The National Weather Service office in Paducah, Kentucky, confirmed that the region it covers, spanning parts of western Kentucky, southern Illinois, southeast Missouri and southern Indiana, just recorded its warmest September 1 through 5 on record. Some of the comparison records at individual stations date back to the late 1800s, making the five-day stretch a standout even against more than a century of local weather history. Four of the region’s five long-term climate stations broke their all-time highest September heat index during the period, a threshold that measures how hot the air actually feels once humidity is factored in alongside temperature. The event unfolded just as air conditioning demand typically starts easing for the year, catching some households and public buildings less prepared than they would have been in the middle of summer.
Cape Girardeau’s Heat Index Held Above 105 for 14 Hours
Cape Girardeau, Missouri, set its all-time highest September temperature during the stretch and logged 14 separate hours with a heat index at or above 105 degrees. For comparison, the city had recorded just one hour total at that threshold across every September from 1996 through 2025, meaning the five-day event alone produced fourteen times the extreme-heat exposure the city had seen in the previous three decades of Septembers combined.
The National Weather Service’s own accounting, posted in its Early September 2026 heat wave summary, framed Cape Girardeau’s numbers as the clearest single example of how far outside historical norms the event pushed conditions across the region. A heat index sustained above 105 degrees for that many consecutive hours falls within the range where the National Weather Service warns of a high risk of heat cramps and heat exhaustion from prolonged exposure or physical activity outdoors.
Poplar Bluff and Mount Vernon Set Their Own Marks
Poplar Bluff, Missouri, logged 20 hours with a heat index of at least 105 degrees during the same window, compared with 13 hours total across every September from 1997 through 2025. Mount Vernon, Illinois, reached 100 degrees on five consecutive days, an unusually long stretch of triple-digit heat for a month when average highs typically sit in the 70s and 80s across the mid-Mississippi Valley. Both totals reflect a pattern seen throughout the region during the event, in which the number of extreme-heat hours logged in five days exceeded what individual stations had accumulated across entire prior decades of Septembers.
Paducah’s Streak Reached Back to 2002
Paducah itself topped 95 degrees for five consecutive days, the city’s longest such streak in the month of September since 2002. The city also recorded four consecutive days with a dew point above 75 degrees, breaking the previous September record of three consecutive days set back in 1991, according to a recap from West Kentucky Star citing the same National Weather Service data. A sustained dew point that high adds a level of mugginess more typical of the Gulf Coast than the Ohio Valley, and it is a major reason the heat index readings ran so far above the raw air temperature throughout the event. High dew points also limit how much the air cools off overnight, which meant afternoon heat had less time to dissipate before the next day’s warmup began.
Evansville’s Streak Reached Back Nearly a Century
Evansville, Indiana, reached at least 98 degrees on five consecutive days, its longest such streak in the month of September since 1925, placing the event alongside the region’s most extreme early-autumn heat waves on record. On September 5 alone, high temperatures reached 100 degrees across the entire region covered by the Paducah forecast office, with many locations posting their warmest September day since 1954. A streak comparison reaching back a full century underscores how far outside the region’s typical early-autumn pattern this particular heat wave pushed, since 1925 predates the vast majority of the area’s modern digital weather-recording infrastructure. Consecutive-day streaks of extreme heat are generally considered more dangerous from a public-health standpoint than a single record-hot day, since the body has less opportunity to recover overnight and indoor spaces without air conditioning have less time to cool down between one hot afternoon and the next.
An Extreme Heat Warning Covered the Region for Five Days
The National Weather Service kept an Extreme Heat Warning in place across the region for all five days of the event, a designation normally reserved for the height of summer rather than the opening week of September, when air conditioning use is typically winding down for the year. The extended warning period reflected forecasters’ concern that the combination of high temperatures, elevated humidity and an early-September calendar date, when many people are less prepared for extreme heat than in July, raised the risk of heat-related illness even for residents accustomed to hot summers in the region. Public health officials in the region generally use these warnings to urge residents to check on elderly neighbors, limit strenuous outdoor activity to the coolest parts of the day and stay hydrated, guidance that applies just as much to an unseasonable September event as it does to a typical July heat wave.
The region’s mix of river towns along the Mississippi and Ohio rivers, along with more rural farming communities spread across the four-state area the Paducah office covers, meant the heat wave’s impact varied by location even as the underlying records were set on a regional basis. Households across the area were still running air conditioning systems at full capacity during the event, a stretch of demand that in a typical year would already be tapering off by early September.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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