The New Year marched in with Mummers in Philadelphia -- including paraders dressed as Saddam Hussein and Martha Stewart -- while a huge crowd gathered for the Rose Parade marveled at petaled spectacles including water-squirting elephants and a bubble-blowing octopus.
Others marched to their own drummers and took part in a different New Year's Day tradition: jumping into bone-chillingly cold water for a quick "polar bear" swim.
But some people had to put their celebrations on hold as a snowstorm hit the West Coast, shutting down a 90-mile stretch of Interstate 5 in Northern California and knocking out power for thousands of people.
About 12,000 elaborately costumed men and women strutted through Philadelphia in the annual Mummers Parade, where many of the string bands strum "Oh Dem Golden Slippers."
This year's party along Broad Street featured people dressed like Philadelphia Flyers hockey players and a shackled Saddam.
Stewart, and the FBI bug found in Philadelphia Mayor John Street's office during the last election campaign, also came in for spoofs from the parasol-waving participants.
"The crowd was very welcoming to us and it felt great," said Peter Broomall, head of the Broomall String Band.
About 800,000 spectators gathered on the streets of Pasadena, Calif., to cheer marching bands and fantastical floats during the 115th annual Tournament of Roses parade.
"I've never been to a big parade before, so it's kind of exciting," said 12-year-old Sydney Brouillette of Lafayette, Ind. Her favorite float was a sunken ship covered with sea animals, including the giant octopus that waved its arms and blew bubbles.
The Grand Marshal's trophy went to the "Springtime Symphony" float, which had eight waterfalls and giant animated woodpeckers, owls and other creatures.
But the most thunderous applause went to military bands and patriotic floats, including one that featured a massive Statue of Liberty and another carrying a statue of Abraham Lincoln made from rice, sesame seed and shredded coconut.
The 23 marching bands, 49 floats and 25 equestrian groups were led by grand marshal John Williams, the conductor who composed the music for "Star Wars" and many other popular films.
While many parade-goers had huddled and shivered in the overnight cold to reserve prime viewing spots, other people stripped to swimsuits and pretended they were polar bears, including hundreds who took quick dips into Lake Michigan at Milwaukee and Lake Minnetonka outside Minneapolis.
About 500 swimmers braved Boston Harbor -- water temperature 42 degrees Fahrenheit -- then dashed back to hot showers and saunas as about 1,500 bundled-up spectators cheered them on for the 100th consecutive New Year Polar Plunge.
"It's the biggest adrenaline rush you'll ever get," Dennis Guilfoyle, 32, of Dedham, Mass., said later as he and his friends warmed up in a pub.
Most of the celebrating was over in New York City, where an estimated 750,000 people had gathered in Times Square for the annual New Year's Eve festivities.
The revelers were ushered away from Times Square as quickly as possible so sanitation workers could clean up the estimated 28 tons of party hats, noisemakers, confetti, paper streamers and other trash. By daylight, the streets were clean and reopened to traffic.
The holiday was a washout for many along the West Coast, where rain drenched the San Francisco and Napa Valley areas, and wind knocked out power to about 100,000 homes and businesses. A mudslide closed southbound lanes of Highway 17 between Santa Cruz and San Jose.
The storm caused whiteout conditions in Northern California, closing a 90-mile section of I-5 between Redding and Yreka for several hours in the morning. It was the third time this week that snow closed the highway.
Up to 5 feet of snow was possible in the mountains of the Sierra Nevada ringing Lake Tahoe, the National Weather Service said.
In Oregon, snow around Portland made stretches of I-5 around the city "if not completely impassable, then temporarily blocked because of cars that have spun out," said Dave Thompson, a spokesman for the Oregon Department of Transportation. For the first time in years, chains were required on all 300 miles of I-5 through the state.