Statutory corporations and departments, as well as banks and other private businesses also closed at 1:00pm.
Officials of the National Emergency Management Agency (NEMA) urged residents to take the necessary precautions to protect life and property.
Rain bands from Tropical Storm Isaac are already being experienced in the islands as the storm moves towards the Lesser Antilles.
At 11 a.m. The National Hurricane Center (NHC) said Isaac was moving west at 21 mph with maximum winds of 45 mph and the latest advisory indicated that Isaac was expected to become a hurricane later today.
According to the latest forecast models from the Hurricane Centre, Puerto Rico, Haiti, the Dominican Republic, Cuba and the US and British Virgin Islands could also experience heavy flooding, mudslides and rainfall.
The NHC report said that hurricane watches are in effect for Puerto Rico, the U.S. and British Virgin Islands and the Dominican Republic.
Isaac is the ninth tropical storm of the 2012 Atlantic Hurricane season.