Heat lightning, also known as silent lightning, summer lightning, or dry lightning, is a misnomer used to describe the faint flashes of lightning on the horizon or other clouds from distant thunderstorms that do not appear to have accompanying sounds of thunder. The term "heat lightning" is commonly used to describe lightning from a distant thunderstorm that is too far away to see the actual cloud-to-ground flash or to hear the accompanying thunder.
The actual phenomenon that is sometimes called heat lightning is simply cloud-to-ground lightning that occurs very far away, with thunder that dissipates before it reaches the observer. At night, it is possible to see the flashes of lightning from very far distances, up to 100 miles (160 km), but the sound does not carry that far. The flashes of light are real lightning strikes from a thunderstorm, but those thunderstorms can be quite far away, which is why the thunder is not heard. Heat lightning is not caused by hot and humid conditions, as many people believe, but rather by distant thunderstorms.
