SAN JUAN, Puerto Rico (AP) — Hurricane Ernesto barreled toward Bermuda on Thursday after leaving hundreds of thousands of people in Puerto Rico without power or water as sweltering heat enveloped the U.S. territory, raising concerns about people’s health.

A hurricane warning was in effect for Bermuda, with Ernesto expected to pass near or over the island on Saturday. The Category 1 storm was located about 635 miles (1,025 kilometers) south-southwest of Bermuda early Thursday. It had maximum sustained winds of 85 mph (140 kph) and was moving north at 13 mph (20 kph).

“I cannot stress enough how important it is for every resident to use this time to prepare. We have seen in the past the devastating effects of complacency,” said National Security Minister Michael Weeks. Ernesto was forecast to become a major Category 3 hurricane on Friday and drop between four to eight inches of rain in Bermuda with up to 12 inches in isolated areas.

“All of the guidance show this system as a large hurricane near Bermuda,” said the National Hurricane Center in Miami. Meanwhile, the spinning storm on Thursday was generating southern winds in Puerto Rico, which have a heating effect as opposed to the typical cooling trade winds that blow from the east. “We know a lot of people don’t have power,” said Ernesto Morales with the National Weather Service as he warned of extreme heat and urged people to stay hydrated.

Nearly half a million of 1.4 million customers remained in the dark .