If you have ever heard or seen a thunderstorm, you most likely have seen flashes of lights through your windows, often reflecting off the walls in your home. What you saw was an electric current in the form of a bright flash of light that was produced during the thunderstorm, after it built up inside the thunderclouds. You may see just one brief flash of light, or several flashes that occur one right after another.
During a thunderstorm, raindrops often freeze inside a thundercloud. When these frozen raindrops bump into each other, they cause an electric charge that eventually fills up the cloud. These positive and negative charges (protons and electrons) form on the ground below the thundercloud, which creates the electric current causing the lightning flashes. Lightning that occurs between clouds is known as cloud-to-cloud lightning, and lightning between the cloud and ground is known as cloud-to-ground lightning.
The most important thing to remember is that lightning is extremely dangerous on impact, so when you hear a thunderstorm you should find shelter immediately --- either inside a sturdy building or a vehicle as a last resort. Stay indoors, away from windows, doors and any water inside your home. If you are unable to find shelter and must remain outdoors, stay far away from water, metal, fences, trees, phone poles and clotheslines. If you are with a group of people, try to stay at least 15 feet away from each other until you can find shelter.
The bright, brilliant flashes of lightning are similar to snowflakes in that no two will be the same size and shape. Their appearance is based on how much electric charge is in the thundercloud. If you see a flicker of flashing lights, what you are seeing is more than one bolt of lightning, one right after the other. Lightning moves at an astounding 62,000 miles per second, which is one-third the speed of light, and has temperatures between 15,000 and 60,000 degrees Fahrenheit --- temperatures that are hotter than the surface of the sun.