Wild weather! Check out these amazing pics of thunderstorms from around the world...
They're caused by a quick rush of hot moist air which rises up into the atmosphere. As the warm air gets higher it cools down and forms a massive cloud.
Weather experts call this type of storm cloud a cumulonimbus - you can usually spot one brewing as they're pretty big!
Thunderstorms get their name from the rumble that you can hear when lightning strikes - sometimes it sounds like loud clap or crack.
The noise is caused by the formation of lightning, a bolt of bright electricity that you can see in the sky.
Lightning can travel really fast - up to a mega 140,000 miles an hour! Speedy!
And it's not only fast: each bolt can contain up to one billion volts of electricity and can be up to five times hotter than the surface of the sun.
It's no surprise that the flashes can be dangerous - each year around 2000 people around the world are killed after being hit by a lightning bolt.