Hurricane Chris strengthened on Wednesday off the US East Coast, with maximum winds of 155km/h (100 miles per hour), on an expected course towards Canada's Newfoundland province.

The center of the storm is expected to pass near southeastern Newfoundland on Thursday, when it will likely become a strong post-tropical cyclone, said the National Hurricane Center in Miami.

It cautioned that swells generated by Chris, which was 440 miles east-northeast of Cape Hatteras, North Carolina, "could cause life-threatening surf and rip current conditions" along the coast of North Carolina and the mid-Atlantic states.

Chris on Tuesday became the second hurricane of this year's Atlantic season.

Last year was especially devastating with hurricanes Harvey, Irma and Maria tearing deadly paths through the Caribbean and southeastern United States.