Steven Sezna, age 10, of Rome, New York, for his question:

What exactly is heat lightning?

When a thunderstorm rages overhead, we expect each flash of lightning to be followed by a roar of thunder. But heat lightning seems to be some¬thing different. The flash is a great cloud of light, instead of a flashing streak. And usually we don't hear any thunder. Nevertheless, heat light¬ning really does come from a flashing, roaring thunderstorm.

Sometimes a storm rages in another part of the sky, perhaps more than ten miles away. Then the streaks of lightning are hidden inside the dis¬tant thunderhead. But their flashes light up the clouds and we see them as great sheets of light. We call it heat lightning because neighboring thunderstorms tend to make the weather hot and humid. We don't hear the thunder that goes with heat lightning because the sound fades away before it reaches our ears.