ST. LOUIS, MISSOURI — Forecasters say there are still several days of hot weather left in the pattern, but from a heat index and humidity standpoint, there is a good chance today, Tuesday, September 15, will be the hottest day remaining this season across a massive stretch of the country. Widespread 100-degree-plus heat index values are expected from Texas through central Illinois and Indiana this afternoon and evening, according to a map from BAMWeather valid Tuesday, September 15, at 4:00 p.m. EDT, with St. Louis topping the region at a scorching 111 degrees.
Today Likely the Hottest Day Left This Season From a Heat Index Standpoint
While the broader pattern is expected to stay hot for several more days, forecasters singled out today as the day most likely to deliver the highest heat index readings of the remaining season, driven by a combination of high humidity and elevated temperatures layered on top of one another. That combination, rather than the raw air temperature alone, is what pushes heat index values well above 100 degrees across such a broad footprint of the country, from the southern Plains through the Ohio Valley.
St. Louis Tops the Region at 111 Degrees as Illinois and Missouri Bake
The single hottest reading on today’s map belongs to St. Louis, where the heat index is forecast to reach 111 degrees this afternoon, the highest value plotted anywhere on the outlook. Nearby communities are close behind, with Jefferson City, Missouri, forecast to hit 104 degrees, while across the river in Illinois, Springfield is also expected to reach 104 degrees and Peoria climbs to 100 degrees. The core of today’s most extreme heat index values sits squarely over this Missouri-Illinois corridor, making it the epicenter of today’s heat threat.
Texas and the Southern Plains See Widespread Triple-Digit Heat Index Readings
Farther south and west, a broad swath of Texas and the southern Plains remains locked in triple-digit heat index territory as well. Dallas is forecast to reach 108 degrees, with Waco and Wichita Falls both expected near 104 degrees and Tyler climbing to 106 degrees. To the northwest, Oklahoma City checks in at 102 degrees, while Wichita, Kansas, reaches 99 degrees and Topeka sits at 90 degrees, marking the northern edge of the day’s most intense heat across the Plains.
Deep South Cities From Memphis to Nashville Push Past 100 Degrees
Across the Deep South, today’s heat index map shows another wide band of 100-degree-plus readings stretching from Louisiana through Tennessee. Shreveport, Jackson and Alexandria are all forecast to reach 106 degrees, while Little Rock climbs to 108 degrees and Memphis follows closely at 106 degrees. Farther east, Nashville is expected to hit 108 degrees, with Huntsville at 106 degrees and Chattanooga at 102 degrees, while Knoxville comes in slightly cooler at 99 degrees as the terrain rises toward the southern Appalachians.
Alabama and Georgia See Heat Index Values Near or Above 100 Degrees
Heat index values remain elevated across much of Alabama and Georgia as well, with Birmingham and Montgomery both forecast to reach 102 degrees this afternoon. Atlanta is expected to come in a bit lower at 95 degrees, while Augusta climbs back to 99 degrees and Savannah, closer to the coast, sits at 93 degrees, reflecting the moderating influence of onshore flow along the Georgia coastline.
Heat Index Values Ease Toward the Upper Midwest and Ohio Valley
The most extreme heat index readings begin to taper off toward the northern and eastern edges of today’s outlook. Indianapolis is forecast to reach 102 degrees, with Evansville running hotter at 108 degrees and Louisville at 104 degrees, while farther north, Cincinnati sits at 99 degrees, Dayton at 90 degrees and Columbus at 93 degrees. In the Upper Midwest, conditions moderate considerably, with Chicago forecast at 88 degrees, Cedar Rapids at 75 degrees, Des Moines at 73 degrees and Lincoln, Nebraska, coming in coolest of all the plotted cities at just 66 degrees, while Youngstown, Ohio, checks in at 82 degrees toward the northeastern edge of the outlook.
What to Expect as the Heat Pattern Continues Beyond Today
Even with today expected to mark the peak from a heat index perspective, forecasters cautioned that the broader hot pattern is not finished, with several more days of hot weather still ahead across much of the central and southern United States. Residents across the highlighted corridor, from Texas through the Ohio Valley, should continue taking precautions against heat-related illness during the hottest parts of the afternoon and early evening, even as the most extreme triple-digit heat index readings are expected to gradually ease heading into the back half of the week.
