For a Thunderstorm to form you need a cumulonimbus cloud, usually producing gusty winds, heavy rain and sometimes hail. The basic ingredients used to make a thunderstorm are moisture, unstable air and lift. You need moisture to form clouds and rain. You need unstable air that is relatively warm and can rise rapidly. And that forms a sever thunder storm.
In Stoughton 2005 There was an outbreak of 28 F1-F4 tornado's all the tornado's were formed by a severe thunderstorm and its remember for killing 1 person and cost 42.5 million dollars in damage.
In dasoto Lauisianna 1900 a F4 tornado hit it killed 18 peaople and cost 1million dollars and the reasonis it cost less because the stuff is cheaper back then.
To prepare for thunderstorms we use lightning rods and now we know to go the bottom floor that's how we prepare for thunderstorms we also have the inter web to see the news . LInks