The first tropical storm of the season is threatening to morph into a hurricane by July 4 as it spins up the US East Coast.
Arthur, as the menacing storm has been named, may jeopardise many people’s holiday plans as it barrels north-eastwards.
It is expected to graze North and South Carolina before easing as it tracks into the North Atlantic Ocean.
Meteorologists expect the ferocious storm to pack winds of up to 85mph and dump up to 10 inches (25cm) of rain, although the heaviest downpours will be out to sea.
It is forecast to pass far enough away from Washington not to disrupt the city’s Independence Day celebrations, including the traditional fireworks display on National Mall.
Arthur is currently lurking off the east coast of Florida as a tropical storm and is moving at around 6mph.
Wind speeds have been picking up, from 40mph gusts on Tuesday to 85mph by Wednesday morning.
The National Weather Service issued a hurricane watch for North Carolina, stretching from Bogue to the Oregon inlet, including Pamlico Sound.
It warned of “life-threatening” conditions for surfers, especially near piers and jetties.