Most of Belmar will be under water by 8 p.m. Monday, officials said.
And during the height of flooding, emergency vehicles will be cut off from accessing many parts of town, Mayor Matt Doherty said.
"If you're going to get out, now's the time to do it," Doherty said.
By high tide, which is predicted for 8:09 p.m., Mayor Matt Doherty said roughly 75 percent of the borough will be flooded.
The most affected areas are expected to be Ocean Avenue west to B Street and anywhere along the Shark River, he said.
The tide will be more than four feet higher than a typical high tide for the Shark River Inlet due to the full moon. And that's not even accounting for the storm.
Major flooding along Route 35 has already closed a portion at 16th Avenue, and Inlet Terrace was taking water, Doherty said.
Doherty said that the window for evacuation was closing fast for any residents who didn't get out by 12 p.m. Monday, as the borough had ordered on Sunday.
At 2:30 p.m. Main Street was still open for traffic and no serious flooding was visible.
Doherty, who said he was staying in Belmar for the storm, said safety was the borough's top priority.
"We'll deal with the damage later," he said.