WFMY News 2 meteorologist Eric Chilton answered our inquiry.
VERIFY PROCESS
"People use the term loosely, and because of its name, they think it is based on temperature and humidity. The truth is that heat lightning does not actually exist," Chilton explained.
He said the flashes you associate as "heat lightning" are flashes of real lightning from a distant thunderstorm. The sound of thunder does not travel all the way up to where you're observing the lightning.
"You can see lightning from a thunderstorm up to 100 miles away, but unless you're within 10 to 15 miles of the storm, you probably won't hear the thunder."
Lightning can happen at any time of the year, even in the winter, as long as cold air and hot air come together.
VERIFY CONCLUSION
Heat lightning is a misnomer. Lightning is lightning, and some of it is just too far away for you to hear the thunder that goes with it.