In the United States, Hurricane Irene's strong winds and heavy rains hit the eastern coast early on Saturday. Though it has lost some strength but still capable of affecting tens of millions of people with floods and power supply disruption.Forecasters at the National Hurricane Center downgraded Irene to the weakest category for hurricanes with winds at 150 kilometers per hour in the early morning hours but cautioned that the storm would remain a hurricane as it moves into the heavily populated corridor around Washington. A hurricane warning has been issued for New York and much of the eastern U.S. coast.New York, Mayor Michael Bloomberg has ordered the city's first ever mandatory evacuation. Some quarter-million people have been told to leave their homes in low-lying areas of the city, including the Wall Street financial district. In another first, New York's entire public transit system, including subway trains and buses, will shut down today. All three of New York's major airports will also shut down starting at mid-day.Airlines have already canceled hundreds of flights elsewhere on the east coast, and train services in parts of the eastern region have been suspended.Irene is the first hurricane to seriously threaten the United States in three years. It has already killed at least one person in Puerto Rico and two in the Dominican Republic, and also destroyed homes in The Bahamas. President Barack Obama has described it as an extremely dangerous and costly storm. He said the nation has to be prepared for the worst. He returned to Washington late Friday, leaving his vacation in Massachusetts a day earlier than planned.The threat of the hurricane also led organizers in Washington to postpone Saturday's dedication of a memorial to civil rights leader Martin Luther King, Jr.