A man carries his dog as he wades through flood waters during Tropical Storm Irene in the Rockaway beach section of Queens, New York August 28, 2011. [Photo/Agencies]

NEW YORK - New Yorkers faced a hellish commute on Monday and millions of Americans throughout the northeastern United States were left in the dark and flooded after Hurricane Irene battered the region before moving into Canada.

Downgraded to a tropical and then a post-tropical storm, Irene pelted eastern Canada with rain and 50-mph (80-kph) winds after killing 20 people in the United States. It cut power to five million homes and businesses and choked towns with floodwaters.

New York subways and air travel at major airports were due to slowly regain service starting at 6 am but there were expected to be delays and overcrowding. Most of the commuter rail services feeding the city from the north were out indefinitely.

Wall Street was largely unaffected as was Ground Zero, where the 10th anniversary of the September 11 attacks is soon to be observed. Financial markets would be open for normal trading, but volume is expected to be low.

The National Tennis Center in Queens escaped serious damage and the US Open was due to start on Monday as scheduled. A football game between the New York Giants and New York Jets was also due to go ahead on Monday evening at the Meadowlands stadium in New Jersey, despite forecasts that flooding in the state could get worse in the coming days.

Suburban New Jersey and rural Vermont were hit particularly hard. Both states were inundated with rain after an unusually wet summer season left the ground soaked and rivers swelled even before the storm rumbled through.

"It's very serious for us at the moment in Vermont. The top two-thirds of the state are inundated with rapidly rising waters, which we anticipate will be an issue for the next 24 hours," said Robert Stirewalt of the Vermont Emergency Management Agency.

The state's many waterways were overflowing, prompting hundreds of evacuations, and some 40,000 to 50,000 people were without power. New Jersey Transit said most rail service would remain suspended until further notice, though some bus service would resume on a limited basis.

In New Jersey, Governor Chris Christie said "we dodged a bullet" after dire predictions failed to produce a catastrophe. But he urged people to stay home from work as the state recovered and pieced together its battered transit system.

"If you don't have to go to work tomorrow, don't go to work tomorrow," Christie told a news conference. "Tomorrow is going to be a very difficult day to travel around the State of New Jersey."