Hurricane Marco and Tropical Storm Laura have torn through the Caribbean and Gulf of Mexico, forcing thousands of coastal residents in Louisiana and Cuba to flee and flooding roads in Haiti's capital, with damage across the region expected to worsen this week.
Marco, which strengthened into a hurricane on Sunday with sustained winds of 120km/h, is forecast to make landfall along the Louisiana coast on Monday.
Laura, which hit the Dominican Republic and Haiti earlier on Sunday before striking Cuba on Sunday evening, is forecast to strengthen into a hurricane on Wednesday before making landfall in Texas or Louisiana on Thursday.
US President Donald Trump issued a disaster declaration on Sunday for Louisiana before the storms. He had issued a similar declaration on Saturday for Puerto Rico, which suffered extensive rains from Laura.
Louisiana Governor John Bel Edwards warned the state's residents that tropical storm-force winds would arrive by Monday morning and they should be ready to ride out both Marco and Laura if they did not leave by Sunday night.
Laura could strengthen into a category two or three hurricane and move west, closer to Houston, the fourth-largest American city, said Chris Kerr, a meteorologist at DTN, an energy, agriculture and weather data provider.
In the Dominican Republic, at least three people died, including a mother and her seven-year-old son, due to collapsing walls.
Laura left more than a million in the country without electricity and forced more than a thousand to leave their homes.
In Port-au-Prince, videos on social media showed people wading waist-deep in muddy water in some of the worst flooding the Haitian capital has seen in years.
Haitian authorities reported five deaths, including at least two people swept away in flooding and a 10-year-old girl crushed when a tree fell on her home.
In Cuba, many residents in the eastern city of Baracoa were leaving their homes on Sunday and heading to shelters or safer buildings on higher ground.
Back-to-back hurricanes arriving at the US coast within days could result in a prolonged period of hazardous weather, the National Hurricane Center said.
A spokesman said the Federal Emergency Management Agency was prepared to handle back-to-back storms, pointing to 2004 when four hurricanes took aim at Florida in a six-week period.
Australian Associated Press