Hurricane Dorian had strengthened into a powerful Category 5 storm as it bore down on the Bahamas Sunday morning with maximum sustained winds of 160 mph. More than 20 million Americans could feel the storm’s impact within a few days.

Preparations are under way to prepare for the massive storm. The hurricane is expected to slam into parts of the northwestern Bahamas by Sunday. Storm surges there could raise water levels 15-feet above normal.

As of 8 a.m. ET Sunday, Dorian’s center was just 35 miles east of Great Abaco in the Bahamas and about 225 miles east of West Palm Beach, Florida, the National Hurricane Center said. The storm was moving west at about 8 mph.