Bill Nye the Science Guy (1993) : 5x16

Storms are big, loud, and often accompanied by rain, snow, sleet, or hail. Where do these wild, dangerous, and necessary tornadoes, hurricanes, and thunderstorms come from? Storms happen when huge different air masses collide. Along the border of these air masses, water vapor condenses into clouds, strong winds form, and the clouds rub against each other with the ground often becoming electrically charged waiting to send lightning bolts across the sky. What starts out as a placid summer day turns into two air masses boxing it out 10,000 meters up.