Several states in the south of the US have declared emergencies as a major tropical storm approaches land.
Florida, Alabama and Mississippi all declared states of emergency ahead of the storm's arrival. It is expected to bring strong winds and extremely heavy rain to southern parts of the US.
Heavy downpours are expected to begin lashing parts of Florida, Louisiana, Mississippi and Alabama today.
The US National Hurricane Center in Miami issued tropical storm warnings for parts of Florida and Alabama, saying tropical storm conditions are possible there by Sunday night.
The governors of Florida, Alabama and Mississippi declared emergencies.
About 5 to 10 inches of rain is expected along affected areas in eastern Louisiana, Mississippi, Alabama, western Tennessee and western Florida. Isolated areas could see as much as 15 inches.
Mississippi residents lined up to fill sandbags to block any encroaching floodwater expected as a result of Alberto.
Tommy Whitlock said sandbagging has become a usual event in his life since he lives next to a creek.
"I'm doing this because every time we have a hard rain, it floods at my house," Whitlock said. "We get water from other neighbourhoods, and water can get up to a foot deep in some places."
Eddy Warner, a retired consultant for a construction company, filled bags while waiting for his nephew to come help transport them home to protect his garage.
"I'm 65 years old and too old to be doing this," he said, laughing.
Alberto - the first named storm of the 2018 hurricane season that officially starts June 1 - is expected to strengthen until it reaches the northern Gulf Coast, likely on Monday night.
The National Weather Service said waves as high as 18 feet (5.5 meters) could pound the popular Gulf beaches in Baldwin County, Alabama, and northwestern Florida on Monday. A high surf warning was in effect from 7pm on Tuesday local time.
At 5am local time on Sunday, the National Hurricane Center in Miami said Alberto was about 330 miles south of Apalachicola, Florida, and moving north-northeast at 13 mph. The storm had top sustained winds of 40 mph.
A subtropical storm like Alberto has a less defined and cooler center than a tropical storm, and its strongest winds are found farther from its centre. Subtropical storms can develop into tropical storms, which in turn can strengthen into hurricanes.
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The downpours could dampen Memorial Day, the unofficial start of the summer tourist season along Gulf beaches. Along with heavy rains and high winds come rough seas and a threat of rip currents from Florida to Louisiana that can sweep swimmers out to sea.
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