Hurricane Erin rapidly intensified into an extremely dangerous Category 5 cyclone as it stayed safely north of the Caribbean islands over the weekend.

Forecasters said Erin should begin to slowly weaken as it increased wind shear. However, it's predicted to remain a major hurricane until late next week.

Storms that ramp up so quickly complicate forecasting and make it harder for government agencies to plan for emergencies. Hurricane Erick, a Pacific storm that made landfall June 19 in Oaxaca, Mexico, also strengthened rapidly, doubling in intensity in less than a day.