Hundreds of thousands of people have been ordered to evacuate the Gulf Coast as Laura strengthened into a hurricane that forecasters say could slam into the US states of Texas and Louisiana as a major storm with ferocious winds and deadly flooding.
More than 385,000 residents were told to flee the Texas cities of Beaumont, Galveston and Port Arthur and still more were ordered to evacuate low-lying southwestern Louisiana, where forecasters said as much as four metres of storm surge topped by waves could submerge entire communities.
Storm Laura was upgraded to a destructive hurricane after causing 20 deaths in Haiti.
"Laura has become a hurricane with maximum sustained winds of 120 km/h, with higher gusts," the US National Hurricane Center reported.
"Significant strengthening is forecast during the next 48 hours, and Laura is expected to be a major hurricane at landfall," it added, warning of storm surges, flooding and torrential rain.
The storm surge "will be accompanied by large and destructive waves" in places, and up to 30 centimetres of rain could cause flash flooding.
The storm has already pounded Cuba, unleashing heavy rain and coastal flooding, after killing at least 20 people, including a baby and an eight-year-old child, in Haiti.
The storm also killed four in the Dominican Republic's capital Santo Domingo.
Storms pose a serious risk to Haiti and the Dominican Republic every year from June to November. Heavy rainfall alone can threaten the poorest residents, many of them living in at-risk zones, near canals or ravines that can be obstructed by debris and quickly overflow.
A woman walks on a bridge near a house damaged by a river after the passing of Tropical Storm Laura in Port-au-Prince, Haiti (AAP) Source: AP
Busy storm season
In Cuba, winds gusting up to 100 kilometres per hour were reported in the capital Havana, and waves of more than three meters battered the Maisi area of Guantanamo province.
The high winds tore tin roofs off homes and downed trees as authorities had evacuated at least 160,000 people in the provinces of Guantanamo, Santiago de Cuba, Granma and Camaguey.
The Atlantic storm season, which runs through November, could be one of the busiest ever this year, with the Hurricane Center predicting as many as 25 named storms. Laura is the 12th so far.
