Top city officials urged New Yorkers to stay indoors and take other precautions as Tropical Storm Isaias brings an “increased threat for tornadoes” to the city.

A tornado “watch” is likely to go into effect from 11 a.m. to 4 p.m., de Blasio officials said Tuesday, meaning a tornado is “already occurring or will occur soon.”

During that time, New Yorkers should seek cover “indoors, on a low floor and away from windows,” Deanne Criswell, commissioner of the Office of Emergency Management, said at a press conference.

People in high rises can go into hallways, she added, and they should “never use elevators” while a tornado watch is in effect.

She also urged people to secure loose equipment if they haven’t already done so.

Winds of 45 to 55 mph and gusts of up to 75 mph are expected from noon to 5 p.m., officials said. Isaias, which made landfall overnight, is also bringing heavy rain to the region.

“Don’t go outside if you don’t need to during the high point of this storm,” Mayor de Blasio said. “When you hear of a tornado warning, it’s not business as usual.

“Please everyone, take this really, really seriously,” he added.

De Blasio initially described the situation as a tornado “warning” but later said he misspoke and the situation would be more accurately described as tornado “watch.”

That’s “less severe than a tornado warning but doesn’t change the basic reality,” he said.