Miami (CNN) -- Katia intensified to a Category 4 hurricane Monday night, churning northwest the Atlantic Ocean and bringing the threat of dangerous rip currents along the U.S. East Coast, forecasters said.
As of late Monday night, Katia was about 450 miles (725 kilometers) south of Bermuda and carried maximum sustained winds of 135 mph (215 kph). It was moving northwest at about 10 mph (17 kph).
But the storm remained well in the Atlantic, with the biggest threat to land continuing to be dangerous rip currents along the U.S. East Coast and Bermuda, according to the Miami-based National Hurricane Center.
"Large swells generated by Katia are expected to affect most of the East Coast of the United States, Bermuda, the Greater Antilles and east-facing beaches of the Bahamas during the next few days," the hurricane center said. "These swells are likely to cause life-threatening surf and rip current conditions."
Hurricane-force winds of at least 74 mph extended 60 miles (95 kilometers) out from the storm's center. Katia's tropical-storm-force winds -- blowing consistently at between 39 and 73 mph -- could be felt up to 205 miles (335 kilometers) out.
Computer models show Katia remaining off the U.S. East Coast as it eventually moves northward, CNN meteorologist Jacqui Jeras said.