Tropical Storm Laura was strengthening in the Caribbean and poised to accelerate into a hurricane by Tuesday while Tropical Storm Marco weakened sooner than expected, sparing the U.S. Gulf Coast from two simultaneous hurricanes, as had been forecast.

Laura traced the southern coast of Cuba on Monday morning, but the brunt of the storm was offshore, helping the largest island nation in the Caribbean avoid serious damage after it killed at least 10 people in Haiti and the Dominican Republic.

It downed trees in Cuba, ripped away flimsy roofs and caused minor flooding on Sunday evening, according to residents and news reports. In Jamaica, there were reports of landslides and flooded roads.

“I slept well last night, except when the wind howled,” Nuris Lopez, a hairdresser, said by telephone from a town in the foothills of the Sierra Maestra mountains in Cuba’s eastern Granma province.

Laura was heading toward the Gulf of Mexico at 20 miles per hour (31 kilometers per hour), according to the U.S. National Hurricane Center (NHC). By Tuesday, it was expected to have reached hurricane strength. By Wednesday night, stronger still, it was expected to hit the U.S. Gulf Coast, the NHC said.

By then, it could be a Category 2 or 3 hurricane on the 5-step Saffir-Simpson scale for measuring hurricane intensity, said Chris Kerr, a meteorologist at DTN, an energy, agriculture and weather data provider.

In Louisiana, Governor John Bel Edwards warned that tropical storm-force winds would arrive by Monday, urging coastal residents to find shelter inland.

Despite Marco’s weakening, with the NHC predicting it would slow to a tropical depression by Monday night, that storm still threatened to soak the Louisiana coast.

“Do not become complacent and remain prepared for whatever comes with this storm and with Laura later this week,” Bel Edwards said in a statement.

The Federal Emergency Management Agency has sent teams to operations centers in Louisiana and Texas.

This year’s hurricane season has been complicated by the coronavirus pandemic, forcing many people to weigh the risks of leaving their homes and potentially exposing themselves to the virus.

Testing for COVID-19 was suspended in Louisiana on Monday and Tuesday, the governor said.