* Washington's 110-year-old seasonal snow record falls
* UN in New York closes, thousands of flights canceled
* New York, Washington, Philadelphia shut down (Recasts, adds details throughout)
By Michelle Nichols and Jeremy Pelofsky
NEW YORK/WASHINGTON, Feb 10 (Reuters) - A second blizzard in a week buried the U.S. Northeast on Wednesday, breaking a century-old snowfall record in the nation's capital, leaving thousands without power and creating a multimillion-dollar mess.
From Washington to Philadelphia and New York, cities largely ground to a halt with governments shut down, public transport scaled back, thousands of flights canceled and some highways closed as snow and powerful winds created whiteout conditions.
The United Nations in New York was closed. But Wall Street and many other businesses plowed on, and one brokerage house, J.P. Morgan Chase, offered cots in conference rooms for workers if they got stuck at work.
"I was as excited as all the school kids when I found out the U.N. was having a snow day. But I don't really get the day off, I am still working from home," said Stephanie Dunstan, 33, an Australian who works for the U.N. Development Program.
The snow did dampen Wall Street trading and was also partly blamed for poor demand at a $25 billion U.S. bond auction.
"People are focusing on how they're getting home because of the snow," said Jeffrey Frankel, president of Stuart Frankel & Co in New York, describing it as "a very dull" stock market.
The National Weather Service said Washington's winter snowfall broke a 110-year-old record with Wednesday's blizzard setting a new mark of 54.9 inches (139.4-cm). Baltimore also set a new seasonal record and Philadelphia was forecast to follow.
Drivers were warned to stay off roads as the snow caused accidents and highway closures. Local media reported multi-car accidents in both Pennsylvania and Virginia.
Thousands of flights were canceled, and airlines relaxed ticket policies to allow passengers to change their plans without penalty, moves that could cloud the outlook for an industry already hard hit by the battered economy.
The blizzard is expected to end early on Thursday, leaving a hefty clean-up bill. New York Mayor Michael Bloomberg said it cost taxpayers $1 million for each inch (2.54 cm) that fell.
U.S. government offices in Washington were also closed for the third straight day, at a cost of some $100 million in lost productivity per day. President Barack Obama had just one item listed on his public agenda, and met at the White House with U.S. black leaders to discuss jobs and the economy.
The U.S. House of Representatives canceled votes for the week. Senate Majority Leader Harry Reid said the Senate would not be in session on Wednesday but would resume work on Thursday. He said he doubted the Senate would have any votes this week. Many congressional hearings were also called off.
In New York, companies allowed employees to leave early and many people worked from home. The busy Metro-North train line between New York and Connecticut said there were almost 40 percent fewer passengers than usual on Wednesday morning.
"It's not that bad out, the snow isn't that bad. It's mostly an excuse not to go to work. People freak out. But now that kids have no school, they have to stay home," said Marc Cadiente, 33, who works at a New York design firm.
Amtrak rail service warned of limited service along its lucrative Northeast corridor. There were no flights in or out of Washington's two major airports and while New York's three main airports were open, most flights were also canceled.
State offices in five major Pennsylvania cities were ordered closed, and New Jersey, Maryland and Massachusetts government offices were shut down, with only emergency and essential personnel required to report for duty.
Some cities, such as Baltimore, ordered all vehicles from the streets except emergency vehicles.
The storm, which has been dubbed "Snoverkill" and "Snowmageddon 2.0," packed strong winds that could cause additional power outages in a region already reeling from a major weekend snowstorm.
Almost 25,000 customers were without power in the Baltimore and Washington areas, according to electric companies, Pepco, Dominion and Constellation Energy Group's BG&E. About 30,000 people were without power in southeastern Pennsylvania, said the local utility PECO.
The storm comes as residents were still trying to dig out from weekend snowfalls of 18 (46 cm) to 32 inches (81 cm) from Washington to southern New Jersey. Some struggled to restock refrigerators and clear fallen trees ahead of the new storm.
Schools were closed across much of the region, and many canceled classes for the rest of the week.
The Washington bus system did not operate on Wednesday and the subway only operated the underground section of its system. In New York commuter train services were increased in the early afternoon to try and get people home before the worst of the blizzard was due to hit in the early evening.
And like Wall Street and some other businesses, on Broadway the show went on.
"The Great White Way is not letting the white snow outside affect the musicals and plays in its theaters," said executive director of The Broadway League Charlotte St. Martin. (Additional reporting by David Alexander and Tim Ryan in Washington; New York bureau; Jon Hurdle in Philadelphia; Editing by Cynthia Osterman)