Most of us have seen those mysterious, silent flashes of light from an almost indeterminate direction, seen only at night. Most people call it heat lightning, but there really is no such thing. That is to say, what we call heat lightning is not actually a different sort of lightning. Rather, flashes of regular lightning are reflected off clouds at night to give us those eerie, silent flashes. It is soundless because it comes from so far away that the sound waves are dampened before reaching our ears.
The light from lightning is a more efficient traveller than sound, and sometimes it bounces off clouds and travels great distances, often well over 50 miles, before reaching our eyes.
This so-called heat lightning is never seen in daylight because sunlight outshines it. But when the clouds are lined up just right, we see the quiet flash of lightning many miles away.