The annual Macy's Thanksgiving Day Parade stepped off this morning, launching the holiday season for millions across the nation, despite a social media campaign aimed to stop it.

At about 9 a.m. the parade began its 2½-mile route at 77th Street and Central Park West, heading south to 59th Street, then onto Sixth Avenue.

According to posts on Twitter, some demonstrators gathered in front of the New York Public Library on Fifth Avenue before heading near the parade route to call attention to race relations after a grand jury in Missouri declined to indict a white police officer who fatally shot Michael Brown, 18, an unarmed black man.

The protesters clashed with police, and the NYPD said seven people were arrested.

The parade, with musical performances and new balloon characters among the floats, marched under clouds, scattered snow flurries and temperatures hovering near 40. There was just a 30 percent chance of precipitation after a winter storm Wednesday that delayed holiday travelers up and down the East Coast. The windchill is expected to make temperatures feel in the 30s, according to the National Weather Service.

A cheer rose from the dense crowd at the corner of Sixth Avenue and West 45th Street as Snoopy's giant white nose floated into view. Camera phones stretched into the air, extensions of arms and eyes over a thicket of capped heads.

Tyce Perry, 9, and his mother, Jeannine Perry, of Kings Park, 37, an elementary schoolteacher waited for their favorite floats.

"We come every year," Jeannine Perry said. "He loves 'Diary of a Whimpy Kid' . . . I just wait for Santa."

Later the Perrys will meet up with family in town from Canada. What are they thankful for? "Friends and family," said Jeannine -- and Tyce chimed in, "and video games!"

John and Patricia Brady, real estate agents from Hampton Bays, each supported a daughter on their shoulders. This was their second time at the parade and the first with their youngest, Sophia, 3. "We just waited until they were old enough."

Leading the parade was Little League pitcher Mo'ne Ikea Davis, 13, of Philadelphia, who threw a shutout for the Taney Dragons during the Little League World Series in August.

The parade featured 16 giant helium balloons, including new characters Paddington bear, Thomas the Tank Engine, Pokemon Pikachu and a lava-spewing Skylander Eruptor.

But as thousands gazed with delight at the balloons, protester Katherine Brezler said she was behind 37th Street barricades when four demonstrators near her were arrested. The scuffles forced the protesters, gathered as part of the StopTheParade march, to regroup shortly after 10 a.m.

"America needs to have a conversation about racism," Brezler said after tweeting videos of what she said were arrests near the parade route. "I'm white and my parents never told me to be uncomfortable with police. But my friends have to be."

"You need to be on the right side of history," said one of her several tweets, as @katastrophe, from the scene.

The protest did not stop the parade.

There, the balloons lined up to meander down Manhattan toward Macy's, at 34th Street and Broadway, where the parade ended.

Joining the festivities were the Big Apple Circus, Before You Exit, William Blake, Sabrina Carpenter, Cirque du Soleil, Hilary Duff, Renee Fleming, Becky G., Lucy Hale, Nick Jonas, KISS, Sandra Lee, The Madden Brothers, Idina Menzel and Miss USA 2014, Nia Sanchez, among others, according to Macy's.

As has been the practice for decades, the balloons were inflated Wednesday along 77th and 81st streets between Central Park West and Columbus Avenue in Manhattan.

The parade will culminate at the flagship Macy's Herald Square, at 34th Street and Broadway.

Santa and the end of the parade neared Macy's at just about noon, as snowflakes dusted the heads of the thousands thronged around the route.

With Ellen Yan and Rosemary Olander