What is Heat Lightning?
Heat lightning is a flash of lighting which appears near the horizon, typically without any accompanying thunder. It is caused by distant storms, and it is commonly associated with summer storms, when the temperatures are warm, hence the “heat” in the name. Heat lightning can be seen in many regions of the world, especially in areas where summer storms are common, and in mountainous regions. It is not the same thing as cloud lightning, also called sheet lightning, a form of lightning which discharges inside a cloud, causing the cloud to light up. Sometimes, heat lightning isn’t lightning at all, but a cloud reflection of lightning from a very distant storm. In other instances, it is regular lightning which has formed far off in the distance, making a flash instead of a recognizable lightning bolt. Especially when dark clouds are massed near the horizon, heat lightning can really stand out, and the absence of thunder can make it seem very eerie. It sometimes takes on a reddish cast, tha
If a lightning strike is a sufficient distance from the observer, sound from the strike will not be heard. These silent bolts are called heat lightning. Lightning bolts produce thunder, but the thunder sound does not travel all the way to the observer if the observer is too far away. The movement of sound in the atmosphere depends on the atmospheric properties of the air such as temperature and density. Because temperature and density change with height, the sound of thunder is refracted through the troposphere. This refraction results in spaces of volume in which the thunder does not propagate through. The sound of thunder often reflects off the earth’s surface. The rumbling sound from thunder is partly due to reflections off the earth’s surface. This reflection and refraction leaves voids where thunder can not be heard. The earth’s curvature also contributes to people far from the strike from not hearing it. Thunder is more likely to be bounced off the earth’s surface before it reach
At this time of year on warm, humid nights, the phenomenon known as “heat lightning” is very common. The sky will seem to flicker with light; and even on a seemingly clear night with stars, you may see flashes. No sound accompanies the flash, although if you are listening to an AM radio, you’ll hear crackles of static at the same time you see the flash. What you’re likely seeing is the light from a distant thunderstorm that is located at too great of a distance for the thunder sound to be heard. The sound of thunder rarely travels more than 10 miles. Other cases can be explained by the refraction (or bending) of sound waves by bodies of air with different densities. An observer may see nearby lightning, but the sound from the discharge is refracted over their head by a change in the temperature, and therefore the density, of the air around him. As a result, the lightning discharge seems to be silent. The term “heat lightning” probably comes from the fact that the effect is most often s
Heat lightning is a name given to a flash in the night sky that occurs when there is a lightning-producing thunderstorm very far away from the observer. Since the storm is often so far away that the lightning bolt itself isn’t observed, and the thunder isn’t heard, the flash in the sky has received a special name. “Heat” probably refers to the fact that this kind of display is often observed on a warm humid night, after daytime heating has triggered thunderstorms — just not near the observer.
