Have you ever heard thunder during a storm? I was always taught that when lightning strikes, it makes a really loud noise and we hear it as thunder. They tell you that in every school in America. But I know better.
Most people don't know this, but there's a dragon living in a cave on the other side of the river where I live. He's a very friendly dragon, but he really hates lightning. So, whenever there's a storm and he sees the lightning, he starts roaring. Every flash of lightning he sees makes him roar. Usually, he'll stay in his cave during a storm and just grumble on about the lightning. But sometimes he takes off into the sky, high above the clouds, letting his voice boom throughout the town. During the winter, he hibernates. There's no lightning in the winter so he can sleep peacefully.