U.S. President Barack Obama has declared an emergency for several states hit by Hurricane Irene, including North Carolina, Virginia and New York, in order to make federal resources available to support response efforts.

The storm, which is no longer a hurricane, still has winds of 55 kilometers per hour. It moved into Canada early Monday, where up to 20 centimeters of rain was possible across Nova Scotia and New Brunswick.

Mr. Obama cautioned Americans, “This is not over.” Severe flooding is expected across much of the northeastern U.S.

The storm killed at least 21 people and paralyzed ground and air traffic in its journey up the eastern U.S. coast. The National Hurricane Center says one of the largest amounts of rain fell in New Bern, North Carolina, where nearly 40 centimeters of rain fell.

Major airports serving New York are expected to re-open early Monday. Much of New York's subway system is expected to be available for many commuters returning to work Monday. Boston's transit authority says most, if not all services will be available Monday.

More than 4 million homes and businesses along the east coast lost electrical power. A Washington area power company dispatched 2,400 people to assist in repair efforts in the region. Some power companies report it may take at least a week to completely restore electrical service.

As the impending storm approached, nuclear power plants were taken offline in Maryland and New Jersey.

As Irene approached Canada late Sunday, Hydro-Quebec reported nearly 250,000 customers near Quebec were in the dark.