It’s a hot night, and it appears lightning is going wild in the dark sky -- but there’s no thunder. What’s going on?
According to the National Weather Service, the term “heat lightning” is commonly used to describe lightning from a distant thunderstorm just too far away to see the actual cloud-to-ground flash or to hear the accompanying thunder.
While many people incorrectly think that heat lightning is a specific type of lightning, it is simply the light produced by a distant thunderstorm, according to NWS.
So it’s not the heat that’s causing the lightning. It’s just distant lightning. But it does tend to happen on warm, summer nights, hence the term “heat lightning.”
As Earth.com notes, heat lightning being so clearly visible from so far away is a matter of reflection, as well as magnification. “Due to light reflecting off of water particles in the moist, humid air, the light is able to spread throughout the upper atmosphere. Over flat terrain, the lightning flashes can be seen up to 100 miles away. While lightning normally produces thunder, the sound of thunder rarely travels more than 10 miles.”
So distant (or nearby) thunderstorms, mixed with humid air, and boom -- heat lightning. The more you know.