How do thunderstorms begin?

Warm air rises, clouds  form as moisture is carried up into the cooler atmosphere. As the air loses heat, the moisture condenses. Clouds are made up of millions of suspended water droplets and ice particles.

Thunderclouds build up electric charges, which are polarized and attracted to their opposites. Heavier negative molecules collect in the bottom of the cloud. When the electric build-up becomes too intense, lightning jumps from the negatively charged bottom of the cloud and strikes a positively charged object -- usually another cloud or the ground.