Category 1 hurricanes mean their peak wind speed is between 74-95 mph. Category 2 is between 96 and 110 mph. A 3 is considered strong and is between 111 and 130 mph. A Category 4 is a very strong hurricane ranging between 131 and 155 mph. Category 5's are rare and have wind speeds over 156 mph.
Category 5's are quite rare. Only 3 have hit the U.S in the 20th Century -- one in 1935, Hurricane Camille in 1969 and Hurricane Andrew in 1992.
Current Hurricane Isabel was a Category 5 in the Atlantic last week and is still very strong, forecast to be near the U.S. East Coast as a Category 3 this week.
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