Subtropical Storm Alberto has made landfall along the northern Gulf Coast, socking the Florida Panhandle with strong winds and rain, the US National Hurricane Centre says.
Alberto's threat to Florida and other south-eastern US states included possible flash flooding, rip currents, gusty winds, coastal flooding and tornadoes, the centre said.
The storm made landfall near Laguna Beach, Florida, stirring up strong surf at beaches along the Gulf and from the Carolinas south along the Atlantic Coast, washing out the unofficial start of beach-going season on the US bank holiday of Memorial Day.
Lifeguards posted red flags at several Gulf Coast beaches, where swimming and wading were banned amid dangerous conditions.
Alberto, the first named tropical storm of the 2018 Atlantic hurricane season, had maximum sustained winds of 80km/h.
The forecast called for heavy rain, life-threatening surf conditions and possible tornadoes in a region stretching from Florida west to Mississippi.
The governors of Alabama and Florida declared states of emergency, and flood-prone areas in those states and in Mississippi kept watch for potentially dangerous rising water.
Many of the areas affected were already soaked by storms that drenched the region last week. The threat of flash flooding could last through the week.
Parts of Georgia, South Carolina and Alabama also will be affected in what could be a harbinger of an active hurricane season.
Alberto will gradually weaken as it moves slowly inland on a northward path placing it in the Tennessee Valley by Tuesday and the Ohio Valley by Wednesday.
The storm is hitting the south-eastern US four days before the official start of the hurricane season.
Australian Associated Press
