A hurricane is an intense low-pressure weather system with winds of 74 or more miles per hour. It is a type of cyclone that generally forms in the tropics. Thunderstorms accumulate into a tropical depression which begins to rotate as it gets bigger over warm tropical water. The tropical depression grows bigger and gains strength, eventually turning into a hurricane. These storms are defined by high wind speeds, with accompanying rain, possible storm surges, flooding and tornadoes.