Florida, facing the Gulf of Mexico on the west, the Caribbean Sea to the south, and the Atlantic Ocean on the east, is the most exposed of all states to tropical storms (i.e. winds 39-74 mph) and hurricanes (i.e. winds greater than 74 mph). Therefore, hurricane season (June - November) is a time of concern to residents of Florida in general and the Keys in particular. The chances of hurricane-force winds striking Florida each year varies from one in 100 at Jacksonville to one in seven at Key West and Miami.

Tropical storms and hurricanes usually originate in the western Caribbean or in the Atlantic, south of the Cape Verde Islands. Warm air masses rising over a large area of warm ocean water results in a drop in air pressure within the air mass causing air around the perimeter to flow into the system inward in a spiraling, counterclockwise direction. A hurricane is formed when the storm grows in intensity and wind speed increases to 75 mph or greater. Relying on tradewinds and other low or high pressure systems to steer them, these storms approach the Caribbean Islands and the southern United States on erratic paths making prediction difficult.

In addition to the destructive power of a hurricane’s winds, serious damage can result from rising water levels as a storm pushes water onto low-lying coastlines. Storm surge is one of the most dangerous aspects of a hurricane to lives and property in south Florida where so much construction has taken place at low elevations along the coastline.

The number of tropical storms varies greatly from year to year, but averages about 1.7 annually. Florida has never gone more than two years without a tropical storm. The longest period since 1885 without a major hurricane was nine years, between 1951 and 1959. Vulnerability to tropical storms varies over the course of the hurricane season. September and October are the peak months of hurricane season.

In August and early September, tropical storms normally approach from the east or southeast, but as the season progresses into late September and October, the region of maximum hurricane activity shifts to the western Caribbean. Most storms that threaten Florida approach from the south or southwest, entering the Keys, the Miami area, or along the west coast.