The Big Apple experienced its second-wettest hour in history as torrential rain drenched the city overnight — with terrifying footage showing straphangers trapped on subways by the freak flash flooding.

“New York City picked up a hair over 2 inches last night — 2.07 inches to be exact — making it the second wettest single hour ever recorded in the city,” FOX Forecast Center meteorologist Christopher Tate told The Post on Tuesday of the rainfall recorded between 6:51 p.m. and 7:51 p.m. in Central Park.

“It was bested only by the nearly 3 inches of rain that fell in New York City during the aftermath of Hurricane Ida in 2021.”

The heavy downpours wreaked havoc across the city with footage showing commuters overwhelmed by floodwaters in various subway stations.

One clip captured a deluge of water pouring into the 28th street station in Manhattan — trapping scores of people on the 1 train line.

“I’m gonna call this one in, I can’t open the doors, it’s not safe,” the conductor can be heard saying in the video.

Other videos appeared to show straphangers standing on train seats to avoid the deluge of water pooling on the floor – as one quipped: “Oh man, I might need a diaper!”

The 1, 2 and 3 trains all ended up being suspended throughout Manhattan as the MTA addressed flooding across several stations. Meanwhile, the Forest Hills-bound M and R trains operated under severe delays as multiple stations reportedly flooded in Queens.

Parts of major thoroughfares in New York, including the Saw Mill River Parkway and Cross Bronx Expressway, were temporarily closed due to flooding as New York’s emergency services agency blasted out a warning on X that parts of the city and mid-Hudson were getting hit with flash floods.

Meanwhile, JFK, LaGuardia and Newark airports were also all struck by lengthy delays as the storm rolled through.

“It was one of the most intense rain storms that the system has dealt with,” said Rohit Aggarwala, the city’s Department of Environmental Protection commissioner – noting the city’s sewer is only made to handle 1.75 inches per hour.

“This is the level of rain that we never expected.”

MTA CEO Janno Lieber told ABC 7 that the city’s sewer system became overwhelmed by rain, which backed up into the subway tunnels and stations.

The backup “popped a manhole” and created the dramatic “geyser” seen in some videos spreading on social media, he said.

“What happened last night is something that is, you know, a reality in our system,” Lieber said. “We’ve been working with the city of New York to try to get them to increase the capacity of the system at these key locations.”

Elsewhere across the city, footage showed water seeping through ceilings, partially submerged cars navigating flooded streets and sidewalks being turned into gushing rivers.   

No death or injuries were reported across the Big Apple, Mayor Eric Adams said.

“I want to thank our first responders, city workers, and everyday New Yorkers for taking our warnings seriously and acting quickly,” Hizzoner said.

“Because people listened — because they stayed off flooded roads and helped protect one another — we avoided greater harm. This is how we meet the moment in a city facing rising climate risks.”

In New Jersey, two women were killed after their car was swept away in Plainfield by flash floods.

Their vehicle was swept into Cedar Brook during the height of the storm and first responders were unable to save them, authorities said.

Gov. Phil Murphy had declared a state of emergency due to the flash flooding and heavy rainfall as he advised people to stay indoors and avoid unnecessary travel.

Cars and emergency vehicles in towns like Somerville and Plainsville were overwhelmed and even partially overturned as the rain battered the region.

In one flooded North Plainfield neighborhood, a house caught on fire and collapsed, possibly due to an explosion, not long after the family inside had evacuated, authorities said. 

Most flash flood watches and warnings expired in parts of New York and New Jersey as the rain moved on overnight, but some roads and streets were still flooded as of early Tuesday.

While rain and scattered thunderstorms were predicted again through Tuesday, Tate said it would be nowhere near as bad as Monday’s dump.

“I think the odds of that are pretty low,” he said.

With Post wires