Building up a storm
The build up of heat and humidity is called "potential energy." The term "potential" means under the right set of conditions, the built up energy may be "potentially" released (often in the form of a storm). Sometimes, when people say the air "feels heavy" what they are referring to is the "potential energy" that is needed to make a good storm. By stepping outside Wednesday night, you actually sense the "potential energy" in the air.
When a storm evolves, the "potential energy" is released in the form of "kinetic energy," or energy that moves. Sometimes this conversion of energy can be very explosive. A Kansas thunderstorm is a great example of this conversion.
We will still have plenty of humidity — "potential energy" — around through at least Thursday morning in Northeast Kansas. The residual "potential energy" may be converted into "kinetic energy" through shower and thunderstorm formation through Thursday morning across much of the area. Later Thursday afternoon, much of the "potential energy" will be gone. This means shower and storm chances will start to go away by Thursday afternoon as a result, and it will not feel as muggy.