Maria is expected to become a dangerous major hurricane as it nears the Leeward Islands in the Caribbean.
The category one hurricane will rapidly strengthen over the next 48 hours and will hit the islands late on Monday, says the US National Hurricane Center.
It is moving roughly along the same path as Irma, the hurricane that devastated the region this month.
Hurricane warnings have been issued for Guadeloupe, Dominica, St Kitts and Nevis, Montserrat and Martinique.
A hurricane watch is now in effect for Puerto Rico, the US and British Virgin Islands, St Martin, St Barts, Saba, St Eustatius and Anguilla.
Some of these islands are still recovering after being hit by Irma - the category five hurricane which left at least 37 people dead and caused billions of dollars' worth of damage.
In its latest update on Monday, the NHC says Maria has maximum sustained winds of 90mph (150 km/h).
The eye of the storm is 100 miles east of Martinique, and Maria is moving west-northwest at about 13mph.
"Preparations to protect life and property should be rushed to completion," the NHC says.
The most southerly point of the Leeward Islands - where Maria will first strike - include Antigua and Barbuda. The latter island was evacuated after being devastated by Irma.