City of Plattsburgh officials closed the gates at the City Beach Wednesday after warnings from the Clinton County Health Department.
"We are reluctantly closing the gates, and we disagree with the decision of the county," Mayor Pro Tem James Calnon said.
Calnon is filling in for Mayor Donald Kasprzak, who is on vacation this week.
The City Beach is not scheduled to officially open until June 23, but the gates were opened last week as temperatures soared into the high 80s and low 90s.
Hundreds of people had been making their way into the beach area despite the locked gates, which promoted the city to act.
After meeting with the county, city officials said they would treat the beach picnic and sand areas as they would any other city park and open them to the public.
They did tell visitors that swimming was not allowed and had police and recreation staff asking people to leave the water.
But with crowds in the hundreds, keeping the water clear of people was a daunting task.
County Health Department officials then told the city this week that by opening the gates they are implying that swimming is allowed, which is in violation of state law.
"I understand why the county is saying that, but we don't agree, and we are not very happy about it," Calnon said.
"We could challenge it, but there is some financially risky business to that, and none of the potential outcomes are very good."
John Kanoza of the County Health Department said state code says that swimming is not allowed without supervision.
"It's tough right now because the weather is so inviting, but there is a reason for every code, and the reason is to reduce risk," Kanoza said.