Hurricane Erin rapidly strengthened offshore to a "catastrophic" Category 5 storm on Saturday, as rain lashed Caribbean islands and weather officials warned of possible flash floods and landslides.

The first hurricane of what is expected to be a particularly intense Atlantic season, Erin is expected to drench Caribbean islands with rain and strong winds but not make landfall.

The U.S. National Hurricane Center (NHC) said in its latest report the storm's maximum sustained winds had increased to 255 kilometers per hour.