The sweltering heat may have had many New Yorkers staying inside or scurrying to the nearest swimming pool, but it did nothing to dissuade the thousands lining Fifth Avenue yesterday in celebration of the 51st annual Puerto Rican Day Parade.

The high of 93 degrees was two degrees shy of the New York City record for June 8, set in 1933, according to the National Weather Service’s Web site.

“We’re all from the island anyways,” a 23-year-old student, Courtney Camacho, said. “It’s this hot in Puerto Rico, so I come no matter what. Everyone is proud of where we come from.”

The parade, which began at 44th Street and ended at 86th Street, drew a heavy police presence, with uniformed officers manning barricades at nearly every cross street along Fifth Avenue.

A spokesman for the police department said arrest numbers would not be released until they could be confirmed overnight. Last year’s festivities were marred when police arrested 208 people amid organizers’ fears that members of the Latin Kings street gang planned to join the parade.

Despite yesterday’s heat, seemingly nothing could dampen the lively mood created by the dozens of floats blaring salsa music and an overwhelming sense of Puerto Rican pride. The city is home to the largest Puerto Rican population outside of Puerto Rico, according to the 2000 census.

Freddy Velez, who was with his band, Orgullo Taino, said he couldn’t remember the last time they hadn’t marched in the parade.

“Once you get into the parade, it gets into you, and you keep on going to it until you die,” Mr. Velez said.

Red, white, and blue Puerto Rican flags lined the streets uptown and were refashioned into shirts, bikinis, shorts, umbrellas, and bandanas. Many state and local politicians walked along the spectator-filled street, including Mayor Bloomberg, Governor Paterson, Governor Corzine, Senator Schumer, and Rep. Anthony Weiner, a likely candidate for mayor in 2009.