US weather forecasters warned Thursday of a subtropical storm forming in the Atlantic that is expected to bring unseasonably heavy rains to the southeastern United States.
The storm system, which unusually comes ahead of the June start of the annual hurricane season, was located 370 kilometers (230 miles) southeast of South Carolina, the National Hurricane Center said.
"Environmental conditions are gradually becoming more conducive for development, and an increase in the organization of the thunderstorms could result in the formation of a subtropical cyclone later today or on Friday," the center said.
"Regardless of development, heavy rain is expected over portions of the coastal southeastern United States for the next several days," it said.
This year's hurricane season, which runs from June 1 to November 30, is shaping up to be one of the least active since the mid-20th century due to the El Nino phenomenon, which generates conditions adverse to the formation of hurricanes, according to experts at the University of Colorado.
The 2014 season was relatively calm, with only six of eight tropical storms reaching hurricane strength.
