Maria is about 590 miles east-southeast of the Lesser Antilles and is packing maximum sustained winds of 50 mph. The storm is moving toward the Caribbean at 19 mph, according to the National Hurricane Center.
Maria is expected to gain strength through the weekend and become a hurricane by late Monday, forecasters said.
Tropical storm watches are posted for Barbados, St. Lucia, Martinique, Dominica and St. Vincent and the Grenadines. The hurricane watch covers Antigua, Barbuda, St. Kitts and Nevis, Montserrat and Guadeloupe.
That means areas devastated by Irma could again be dealing with hurricane conditions by Tuesday or Wednesday.
Maria joins Tropical Storm Lee, which formed earlier Saturday in the eastern Atlantic Ocean.
Lee is spinning about 720 miles west-southwest of Cape Verde
off northwest Africa and packing maximum sustained winds of 40 mph, according to the National Hurricane Center.
Lee isn't expected to gain much strength over the next 48 hours and will likely fade to a tropical depression by Wednesday without affecting land, the center said.
These new Atlantic systems join Hurricane Jose, a Category 1 storm spinning about 480 miles south-southeast of Cape Hatteras, North Carolina.
Jose could bring rain and wind
to the US Northeast early next week.