It’s a two-ingredient recipe! First you need moisture, or water in the air. And second is lift! Something that makes the moisture rise in the sky! Now the question is how do we get the ingredients to react?
The two most common ways are with a front either a cold or a warm front, or sunshine. The front will act like a ramp and send the moisture up in to the sky and the sun heats the ground and that makes the moisture rise and turn into a cloud. As the clouds grows taller the water droplets in the cloud begin to freeze. The higher the cloud gets the more ice pellets it will have inside of it. The ice pellets in the clouds begin to bounce off each other, because of the updraft inside the thunderstorm and that produces an electrical charge. It’s the same idea as rubbing your feet along a carpet and touching a door knob, it shocks you.
Now that’s just a normal thunderstorm. To make the storm severe it has to have one of the following: Winds of 58 mph or more, hail that is 1 inch in diameter, and finally if it produces a tornado.