BELMAR, N.J. — As coronavirus-related restrictions are eased and temperatures climb, people are flocking back to the Jersey Shore.

And with the July Fourth holiday weekend upon us, that's making some people nervous, particularly given the large crowds that have surfaced at some popular shore spots recently and poor compliance with mandated measures to help slow the spread of the virus.

"I am really concerned," said Paul Kanitra, mayor of Point Pleasant Beach, a popular shore town that was unexpectedly overrun by thousands of tourists who swarmed the beach and boardwalk a few weeks ago at a "pop-up party," paying little heed to social distancing or masks.

"We're seeing spikes across the country in states that opened up weeks ago, and while we're doing a good job in New Jersey, there are a lot of people that are way too cavalier about social distancing," he said. "There's inherent risk in all of this."

Large crowds are expected at the shore for the holiday weekend: New Jersey's casinos have reopened, along with amusement rides and water parks. Beaches are open, though at reduced occupancy levels. Restaurants can offer limited outdoor dining, and stores and shopping malls have reopened.

But not everyone is following rules designed to prevent the spread of the virus, including wearing masks and keeping 6 feet (2 meters) apart. In late June, large crowds swarmed D'Jais, a popular oceanfront nightclub in Belmar in scenes reminiscent of pre-pandemic days. Few patrons wore face coverings, and fewer still kept their distance from others on a packed dance floor.

Gov. Phil Murphy saw videos of the packed club and warned the state will not hesitate to reimpose harsher restrictions if people don't behave.

"We cannot let up on our social distancing or our responsibility just because the sun is out," the governor said. "We can't be lulled into complacency and think it's OK to crowd around a bar. That is how flare-ups happen."

Skyler Walker, a woman from Scotch Plains in her early 20s, was on the Belmar beach last week on a sunny day with temperatures brushing 90 degrees.

"I definitely think people people are starting to care less about" the virus, she said. But the face mask she wore on the boardwalk while waiting in line to buy beach badges indicated she does not share that view. "They act like it's over now."

She was at the beach with a friend who is a nurse in a Jersey Shore hospital filled with coronavirus patients. The friend, who would not give her name, was adamant that the virus is not over, based on what she sees at work every day. She is scheduled to work at the hospital on July Fourth.

Michael Scott, another 20-something on the Belmar beach, said he and his friends have modified their behavior this summer, including at nightclubs.

"I try to just hang out with my people," he said. "I'm not all about looking to meet new people. We have a close group of friends that all kind of quarantined together."

Ocean City Mayor Jay Gillian pleaded with residents and visitors to wear masks during the long holiday, including on the boardwalk, noting, "Ocean City is already very crowded."

Although New Jersey's hospitalization rate is down drastically from a peak a few months ago, officials fear hospitalizations for the virus will rise again if people become lax about taking precautions.

"We are especially concerned after the gatherings we saw at the Jersey Shore," added the state's health commissioner, Judith Persichilli. "Individuals were packed together, which raises the risk of spreading the virus."

A big test is happening this weekend with the reopening of eight of Atlantic City's nine casinos. The Borgata is remaining closed due to smoking, drinking and indoor eating bans Murphy imposed on the gambling halls.

Most casinos scan guests temperatures upon entering, hand sanitizer dispensers are placed throughout the premises, and everyone inside must wear a mask.

The first day of operations, on Thursday, appeared to go well, with widespread compliance with virus precautions. In 2 1/2 hours on the gambling floor of the Hard Rock casino, an Associated Press reporter did not see a single person without a mask.