well, hurricane idalia is already causing flooding in some coastal towns, as you can see right here in cedar key, florida. officials are warning of a life-threatening storm surge of up to 15 feet in some areas. just how dangerous, tom foreman, will this search b and which areas will be hit the hardest? joining me now is cnn's tom foreman at the magic wall to explain it all. so, tell me about this storm surge. take a step back with me. how does this work? >> storm surges -- always what it is primarily