NOAA
A hurricane warning has been issued in areas that are bright red and tropical storm warning in areas that are deep red.
"Beach-goers all along the Mid-Atlantic and Northeast U.S. coasts will be at risk from dangerous rip currents Friday through Saturday," Director of Meteorology and hurricane expert Dr. Jeff Masters at Wunderground.com told Business Insider. The threat should diminish by Sunday, he said.
A rip current, or strong channel of water flowing from the shore out to sea, can move up to 8 feet per second, which is faster than any human swimmer, says Masters.
If a swimmer doesn't know the right way to get out of a rip current - by swimming at a right angle to the fast-moving channel - "they may exhaust themselves trying unsuccessfully to swim against the flow," says Masters.
Rip currents kill about 100 people a year, according to LiveScience.
As of now, the storm is now expected to be a category 2 hurricane as it approaches eastern North Carolina, and may become the earliest-known hurricane to make landfall in that state. If you aren't at the beach, here's what Masters says to expect:
Eastern North Carolina will feel the brunt of the storm. Heavy rains are already falling along the coast, and these rains will accumulate to 3 - 5", with isolated amounts of up to 7", through Friday afternoon, causing minor flooding. The bigger threat is coastal flooding due to storm surge, which will peak late night and early Friday morning from Morehead City, NC, to the North Carolina/Virginia border. A storm surge of 2 - 5 feet is expected. This is the same time that winds of hurricane force will potentially affect the coast. By late Friday morning, the winds will fall below tropical storm-force, and the storm surge will subside.
As Arthur accelerates northeastwards towards Nova Scotia, Canada, large waves of 4 - 5 feet will begin to pound coastal Massachusetts on Friday night. Tropical storm force winds of 40 mph may affect Cape Cod and Nantucket, Massachusetts between 10 p.m. Friday and 4 a.m. Saturday, and Nova Scotia, Canada beginning at 5 a.m. Saturday.
NYC will not be directly affected by Arthur, but will get rain Friday afternoon from the trough of low pressure that is steering Arthur towards Nova Scotia.