Throngs of New Yorkers descended onto city beaches and parks to soak up the abundant Memorial Day sunshine – as the unofficial arrival of summer got off to a sizzling start.

Clear skies with very few clouds greeted those who ventured out to city green spaces Monday afternoon, with the mercury reaching 84 degrees at 2 p.m. in Central Park – far warmer than the Memorial Day average of 75 degrees.

“Overall, it’s just an absolutely, almost perfect Memorial Day,” Fox Weather meteorologist Greg Diamond told The Post. “There’s zero chance of rain in the tristate area today … Definitely one of the warmer Memorial Days in recent years.”

Droves of people sunbathed or rode bikes in Central Park, while others hit up the city’s beaches.

“Oh my gosh, it’s the best,” said Amandina Altimare, 29, who went to the Manhattan park with her dog, Bruno. “To have this weekend — Memorial weekend — be so beautiful is what all New Yorkers waited for all winter.”

Altimare, who owns a social media agency, said she and her pooch had to take “full advantage” of the day after her prayers for good weather were answered.

“I prayed and hoped for two weeks for today to be this beautiful,” Altimare continued. “And it happened! Hallelujah!”

Coney Island Beach was also crowded, with revelers getting an early start on the summer season by scarfing down lobster rolls and clam strips.

“Just enjoying the day off,” Sam Johnson, 24, of SoHo, told The Post. “Getting some sun. Trying all the crazy foods.”

Katie Frank, a 36-year-old bartender from Queens, started her day at the New York Aquarium before heading to the sand.

“Today is really crowded compared to what we normally see,” Frank said. “I wouldn’t mind it being a little hotter, but I’m a summer person.”

Monday’s warm weather is expected to continue into Tuesday – with a high of 96 expected in Central Park, which would tie a record set in 1939, Diamond said.

“If we hit 96, not only will it tie the daily record, but it will also be the hottest temperature recorded in the month of May since May 20, 1996, when Central Park also got to 96,” Diamond wrote in an email.

It could also reach a scorching 95 in nearby Newark and surrounding areas in New Jersey on Tuesday.

Most of northern New Jersey, Connecticut and the Lower Hudson Valley will be in the low 90s before a “backdoor cold front” from New England sends the mercury plunging on Wednesday while bringing in cooler air from Canada.

Highs in those areas will drop into the 70s on Wednesday, with temps nearing 10 degrees cooler along coastlines. Wednesday’s expected high in New York – 69 degrees – will feel far cooler than it did a day earlier, Diamond said.

Some rain is expected in New York late Wednesday into Thursday — with another round of precipitation throughout the tristate region to come late Thursday.

Storms will then linger throughout New York and surrounding areas early Friday before clearing out – with temperatures expected in the upper 70s and lower 80s, Diamond said.

The city’s Department of Parks & Recreation, which maintains 14 miles of beaches, reminded beachgoers on Saturday to be safe when hitting up the surf.

“Remember to swim only when lifeguards are on duty,” the agency tweeted while announcing the opening of city beaches. “Lifeguards will be on duty daily from 10 a.m. to 6 p.m.; swimming is unsafe and strictly prohibited at all other times.”

All city beaches, including Brooklyn’s Coney Island and Rockaway Beach in Queens, are free and open to the public.