Lightning is common during the summer months and it is someone most everyone is quite familiar with and experiences quite often. However, fewer people know or understand what heat lightning is even though it may even be more common than the lightning that occurs as a part of a thunderstorm that is easily recognizable and better understood by the general population.
First of all, heat lightning does not simply just occur out of nowhere during hot weather. It is not a type of combustion or another rare weather phenomenon, but instead a weather pattern that occurs frequently but is not always identified correctly.
Extremely hot and humid summer days, especially those in July or August, can commonly be followed by periods of what is known as heat lightning or lightning-induced illumination that is too far away for thunder to be heard. When this phenomenon occurs, the sky will seem to flicker with light; and even on what seems to be a clear night with stars, flashes may be seen. Heat lightning signals that a thunderstorm is occurring in the distance and could be on its way to the area where one sees heat lightning. It is best to be prepared for the potential of weather conditions changing from relatively calm to severe in the near future.
The specific term, heat lightning, most likely was derived from the fact that this sort of lightning effect is most often seen on hot, sultry nights in mid-summer, so the so-called lightning is seen to be directly correlated with hot weather and heat.
Heat lightning can be seen from as close as ten miles away from an actual thunderstorm where it is usually not possible to hear thunder or when the sky is hazy, as is fairly common on hot, humid summer nights, the light from intense thunderstorms as far away as 100 miles can be reflected off a layer of haze and up into the night sky.
To recap, heat lightning is actually light in the sky that appears on a warm to hot evening from a distant thunderstorm that is too far away for thunder to be heard. It is very common in the mid-summer months and by itself is not dangerous, however it can be the signal of an impending thunderstorm that could possibly be dangerous, so if heat lightning is observed, a person should be on alert to the possibility of a dangerous thunderstorm coming their way.