MEMPHIS, Tenn. (WMC) -MEMPHIS, TN (WMC) - There’s an old wives’ tale that on a hot, humid summer night, lightning can happen without a thunderstorm. People often refer to this as “heat lightning.”
The term heat lightning is actually used to describe lightning from a distant thunderstorm that’s too far away to see the actual cloud-to-ground flash or to hear the accompanying thunder.
The term “heat” in heat lighting may have been used to describe the condition in which the flashes are usually seen. The temperatures are these nights are very warm and muggy.
Sometimes mountains, hills, trees, or just the curvature of the earth prevent the observer from seeing the actual lightning flash.
Instead, the flash seen by the observer is light being reflected off higher-level clouds. Also, the sound of thunder can only be heard for about 10 miles from a flash. What you are seeing are flashes from storms in the distance.