Tropical Storm Bonnie formed off the southeastern US coast, forecasters have said, dashing beach plans for some Americans at the start of the long Memorial Day weekend.
Heavy rain was spreading across coastal areas of South Carolina, with the National Hurricane Center warning that the storm could spawn isolated tornadoes later yesterday or early today.
Packing maximum sustained winds of some 40 miles per hour (65 kilometres per hour), Bonnie was located about 125 miles south-southeast of Charleston, South Carolina, at 2100 GMT, according to the latest bulletin from the Miami-based NHC.
Moving to the northwest at about 10 mph, a tropical storm warning was in effect for parts of the state.
"Some additional strengthening is possible tonight as Bonnie moves over the warm waters of the Gulf Stream," the NHC said. "Gradual weakening is forecast on Sunday."
Bonnie was expected to dump up to five inches (13 centimetres) of rain from eastern South Carolina through southeastern North Carolina, it said.
Life-threatening surf and rip current conditions were also possible, the forecasters warned.
Memorial Day -- a public holiday commemorating fallen service members observed Monday -- is considered the unofficial start of summer, with many Americans taking advantage of the free day to head outdoors, including to the beach.
On Friday, US government scientists said more storms are expected during the coming Atlantic hurricane season that begins June 1 and runs through November 30.
The Atlantic could see 10 to 16 tropical storms, of which four to eight could become hurricanes, said the National Oceanic and Atmospheric Administration's (NOAA) Climate Prediction Center.
