Simplify the following text for a Grade 5 native English-speaking person.
Original: Six Atlantic hurricanesâ '' Allen , Andrew , Isabel , Ivan , Dean and Felixâ '' have reached Category 5 intensity on more than one occasion ; that is , by reaching Category 5 intensity , weakening to a Category 4 or lower , and then becoming a Category 5 again .
Simplified: There are no records of a Category 5 hurricane before 1900 . The season with the most Category 5 hurricanes was in 2005 , which had four .