A flash flood warning was in effect for parts of Upper Manhattan and the Bronx through at least 6 p.m. Monday night, as heavy thunderstorms – and globs of hail – continued to drench much of the New York City region.

So far, the bulk of the impact has been concentrated around the northern part of the city and surrounding suburbs, with significant impacts expected to last through the evening commute, according to meteorologists.

As a result of flooding conditions in the Bronx, service on the Harlem and New Haven Lines was temporarily suspended out of Grand Central Terminal. Both lines were experiencing significant delays as of 5:30 p.m. Monday.

Parts of the Major Deegan, the Bronx River Parkway and the Hutchinson River Parkway were also experiencing flooding earlier in the afternoon. And the MTA canceled A train service between 168th Street and Inwood-207th Street as crews removed water from the tracks.

Eric Weglarz, a meteorologist with National Weather Forecasting, said that New York City’s neighborhoods were experiencing close to five inches of rain in just a short amount of time – a recipe for dangerous surface flooding.

“This would have to be the most significant rainfall we've seen since Ida,” Weglarz said, referring to last summer’s Tropical Storm Ida, which paralyzed the region.

“The best message for folks who are out and about is to treat any high water seriously,” he added. “After the flooding, it takes some time to evacuate the water.”

Isolated storms were expected to pass through the area later Monday evening before tapering off around 9 p.m.