As you can see on the graphic, the center of the hot upper level high pressure center is over the Central Plains and Mississippi Valley. That's why the hottest temperatures are there.
Over the next two days, the center will migrate over the mid south yielding highs in the upper 90s in many areas with a heat index 100-105.
However, much like last week, by Thursday and Friday, the high will be shoved out of the way temporarily, allowing another front to work its way into the area.
This increases t'storm chances from Thursday PM through Friday, and will allow the "edge" to be taken off of the temperatures as we head into Saturday.
Very similar pattern and timing to last week!