Tropical Storm Ernesto became a hurricane again Sunday as it churned away from Bermuda and headed further out in the northeastern Atlantic, sending powerful swells toward the U.S. East Coast, generating rip currents associated with at least one death and prompting many rescues.

The National Hurricane Center in Miami said Ernesto’s maximum sustained winds were clocked at 75 mph (120 kph), just barely Category 1 strength. More strengthening was forecast over the next 12 hours, with Ernesto then expected to weaken and become a post-tropical cyclone on Tuesday, the hurricane center said. The storm was centered about 520 miles (840 kilometers) south of Halifax, Nova Scotia, and was expected to pass near southeastern Newfoundland late Monday and early Tuesday.

Swells generated by Ernesto were affecting portions of the Bahamas, Bermuda, the U.S. East Coast as well as the Canadian Atlantic coast.

Life-threatening surf and rip current conditions are likely in these areas during the next couple of days, the hurricane center said. The National Weather Service earlier posted a coastal flood advisory and warned of a high risk for rip currents along the Atlantic Coast through Monday evening, saying they “can sweep even the best swimmers away from shore into deeper water.” A warning extended from Florida to the Boston area and portions of Maine.

In periods of high risk, rip currents become more likely and potentially more frequent, posing a danger to all levels of swimmers, not just i.