Tornadoes

I watc Website that introduces tornadoes, why do we have tornadoes , if it happens now what you must do can let you safe. And in the USA, which always has a lot of tornadoes and a lot of things about it, that's very interesting and also helpful.
I think having tornadoes is about weather, some countries have tornadoes. For example China and Japan have no tornadoes or just a few, so they often think there are none or it doesn't matter. In the USA, some of states have them, so if no one died in a tornadoe, that's Ok, because we can't change our earth, but we can make sure no one died.