In this book, we learn that thunderstorms are formed when warm air rises quickly from Earth into the sky. As the warm air cools, it forms rain clouds called cumulonimbus clouds or thunderclouds. As the warm air continues to rise and cool inside the clouds, it drops water and ice. The water and ice then fall to Earth. You have probably seen bolts of lightning strike Earth during thunderstorms.
Lightning is caused by electricity moving in between clouds or between the clouds and the ground.
The electricity is formed when ice and water particles move around rapidly inside the clouds. As the particles move they become oppositely charged and they separate. The positively charged particles go to the top of the cloud and the negatively charged particles sit along the bottom of the cloud. The negative particles along the cloud bottoms grow large and are attracted to the positive charges on the ground. When the attraction between the different charges becomes strong enough, electricity flows from the cloud to the ground.