Simplify the following text for a Grade 5 native English-speaking person.
Original: The hurricane devastated the islands of Niihau , Kauai , and Oahu with wind gusts exceeding 100 mph ( 160 km\/h ) and rough seas exceeding 30 feet ( 9 m ) in height .
Simplified: The storm caused very bad damage on the islands of Niihau , Kauai , and Oahu . Some wind gusts reached 100 mph ( 160 km\/h ) , and waves were over 30 feet ( 9 m ) high .