The US National Hurricane Center (NHC) said Maria had intensified to a Category Two storm as it approached the French territory of Guadeloupe, the base for relief operations for several islands hit by Irma this month.
"May you continue to be resilient and united as we work together to ensure we're prepared for the storm and ready to continue the rebuilding efforts once it has passed", he said. "All of Puerto Rico will experience hurricane-force winds".
The National Hurricane Center said Sunday that the storm has maximum sustained winds of 75 miles per hour (120 kph).
A hurricane warning is in effect for St. Kitts and Nevis, meaning that "hurricane conditions are expected somewhere within the warning area" and "preparations to protect life and property should be rushed to completion", according to the National Hurricane Center.
Tropical storm warnings were in place in Antigua and Barbuda, Saba and St Eustatius, and St Lucia.
Maria "is expected to produce total rain accumulations of 6 to 12 inches", the hurricane center says, "with isolated maximum amounts of 20 inches across the central and southern Leeward Islands, including Puerto Rico and the US and British Virgin Islands, through Wednesday night". The storm was predicted to bring 6 to 12 inches (15 to 30 centimeters) of rain across the islands, with more in isolated areas.
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Predictions call for it to pass straight over Puerto Rico on Wednesday.
In Florida, people are already preparing for the storm to hit. "This is going to be a catastrophic event".
Maria was expected to bring storm surges of up to 1.8m-2.7m, the NHC said. Schools were canceled for Monday and government employees worked only a half day.
"Our call is for people to evacuate areas that are prone to floods and landslides, in addition to vulnerable structures", Gov. Ricardo Rosselló said.
Further north, Hurricane Jose, a Category 1 storm, is expected to bring tropical storm-force winds of up to 50 miles per hour along the coasts of New Jersey and NY on Tuesday evening, the National Hurricane Center, reports. Tropical Storm Lee formed on Saturday in the Atlantic Ocean, and is headed west, but expected to weaken before making any landfall. It is moving west-northwest at 13 miles per hour (20 kph). It had maximum sustained winds of 85 miles per hour (140 kph).
The following map shows Maria's projected path, according to the National Hurricane Center.
Maria is now the fourth major hurricane of the 2017 Atlantic Hurricane Season and this marks the first time since 2010 that we've had four major hurricanes by this point in the season (September 18).