Hurricanes form over tropical oceans when intensive heat from the sun causes lots of air and water to rise quickly forming thick clouds and heavy rain. While this may be enough to make a storm only when wind speeds exceed 75 mph is it considered a hurricane. To understand how such strong winds form you first need to know a little about air pressure. Even though the air around you seems empty it’s actually full of gases that are quite heavy. You don’t notice the weight of air because you’re so used to it but it places about 15 lbs of pressure on every square inch of your body.