Here are some facts about Category three & four from ERN News:
1. Well built buildings can survive but are likely to experience loss of some or all roofing, windows will likely shatter if uncovered, trees and big branches on trees will come down
2. Storm surge flooding in the area immediately inward from the coastal zone is the greatest danger if people have not evacuated beforehand. Storm surge flooding above rooftops, along with high winds, is generally not survivable.
3. Power lines will come down. There is a danger of electrocution form downed lines if the power has not been cut.
4. Cell phone service will go out in most cases and, like power, not likely be restored for a period of days or longer.
5. Many roads will be blocked with downed poles and trees and might be entirely impassable.
6. Tornadoes are likely to spin up as the hurricane moves in and can cause significant damage, injuries and deaths.. These are usually fast developing with no advance warning other than by sight and sound. Take shelter as you would for any tornado.
7. Fire and police crews will not be able to come and rescue you in most cases while the storm continues to rage. Only when the wind begins to abate will they be able to swing into action.
8. If you are in the hurricane zone, be prepared to survive on your own for at least three days with water, food and a comprehensive firstaid kit.
There are many sites on the internet that can also provide additional guidance.