At least 22 people have died in Central America as Tropical Storm Nate dumped heavy rain across the region.

The storm could potentially strike the Gulf Coast of the United States as a hurricane over the weekend and Louisiana has declared a state of emergency.

The US National Hurricane Centre said the storm could cause dangerous flooding by dumping as much as 15 to 20 inches (38 to 50 centimetres) of rain as it moved over Honduras, with higher accumulations in a few places.

Nate had maximum sustained winds of 40mph (65kph) by Thursday evening and was likely to strengthen over the north-western Caribbean Sea into Friday before a possible strike on the Cancun region at the tip of Mexico’s Yucatan Peninsula at near-hurricane strength.

It could hit the coast near New Orleans over the weekend at hurricane strength, forecasters said.

In Nicaragua, Nate’s arrival followed two weeks of near-constant rain that had left the ground saturated and rivers swollen.

Authorities placed the whole country on alert and warned of flooding and landslides.

Nicaragua’s vice president and spokeswoman Rosario Murillo said that at least 15 people had died due to the storm.

She did not give details on all the deaths, but said two women and a man who worked for the Health Ministry were swept away by a flooded canal in the central municipality of Juigalpa.

Costa Rica’s Judicial Investigation Department blamed seven deaths in that country on the storm and said 15 people were missing as flooding drove 5,000 residents into emergency shelters.

In Louisiana, governor John Bel Edwards declared a state of emergency and mobilised 1,300 National Guard troops, with 15 headed to New Orleans to monitor the fragile pumping system there.

With forecasts projecting landfall in south-east Louisiana on Sunday morning, Mr Edwards urged residents to ready for rainfall, storm surge and severe winds – and to be where they intend to hunker down by “dark on Saturday.”

Louisiana’s governor says Nate is forecast to move quickly, rather than stall and drop tremendous amounts of rain on the state.

State officials hope that means New Orleans will not run into problems with its pumps being able to handle the water.