New York City, New Jersey brought to a standstill by flash flooding

A coastal storm unleashed a deluge of heavy rain on the New York City Tri-State area from late Thursday night into Friday night, leading to flash flooding, stranded motorists, street closures, subway suspensions and hundreds of flight delays and cancellations. Water rescues were reported in neighboring New Jersey.

As the flash flood emergency unfolded, New York Gov. Kathy Hochul declared a State of Emergency across New York City, Long Island and the Hudson Valley, posting on X (formerly known as Twitter), "Please take steps to stay safe and remember to never attempt to travel on flooded roads."

As the heaviest rain ended Saturday morning, a total of 5.90 inches of rain had fallen at New York's Central Park, including nearly 2 inches in an hour between 9:00 and 10:00 a.m. EDT Friday.

There were also reports of more than 9 inches of rain in the Gowanus and Park Slope neighborhoods in Brooklyn.

"One thing I've learned in my almost 20 years at AccuWeather is that it's not only the rain amount but it's how quickly that rain is falling," AccuWeather Chief Meteorologist Jon Porter said. "And when you start getting rain that's coming down 1.5, 2, 3 inches per hour - that's what we saw Friday, that's what we warned about [Thursday] exclusively here [at AccuWeather]. That's when you get big impacts because it's just too much water for the sewer and storm water systems to keep up with."

It has already been a wet month in New York City, and this storm put this month's total rainfall in rare territory. Through 9 a.m. EDT on Saturday, more than 14 inches of rain had fallen in September, making this the second wettest September since records began in 1869. The wettest September stands at 16.85 inches of rain set back in 1882.

The daily rainfall record for Sept. 29 in the city was toppled as 5.48 inches of rain doused Central Park, with the old record of 2.17 inches from 1963 already broken before 10:00 a.m. EDT Friday. In fact, Sept. 29 became the wettest September day on record at John F. Kennedy International Airport as 8.05 inches of rain fell, the National Weather Service said, which kept records starting in 1948.

AccuWeather was the first to forecast flooding in New York City, ahead of the NWS. On Wednesday night, AccuWeather forecasters stated that flash flooding could occur in the area at the end of the week. On Thursday morning, meteorologists added the potential for more serious flash flooding to forecasts, and on Thursday afternoon, said 4-8 inches of rain would lead to life-threatening flooding in New York City.

"It appears that the rainfall from this storm could be New York City's heaviest since Hurricane Ida in 2021," Porter said Friday morning. That tropical rainstorm brought major flooding and more than 7 inches of rain to the city on the first day of September that year.

The remarkable intensity of the rain falling made for a nightmarish morning commute on Friday, disrupting multiple methods of travel into and out of the city.

A map of 24-hour rainfall totals, from 9 p.m. EDT Thursday to 9 p.m. EDT Friday, shows the excessive rainfall amounts across New York City, leading to travel chaos on Friday.

The Metropolitan Transit Authority (MTA) suspended train services at many stations, and there were extensive delays where New York City subway trains were still running on Friday.

"There is only extremely limited subway service available because of heavy flooding caused by rainfall. Service may be suspended on certain stations," MTA said on its website.

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At least one terminal was closed for a time as floodwaters affected LaGuardia Airport. Flight delays had topped 400, and total cancellations also approached 400 at LaGuardia on Friday, according to FlightAware.

Numerous photos and videos posted to social media showed flooding and water flowing across streets, in the subway, on buses and along major thoroughfares.

Tom Winter, a reporter for NBC News, reported that the NYPD and FDNY were responding to numerous flooded basements and even roof and ceiling collapses related to the heavy rain.

The NWS relayed reports of flooding across all five of the boroughs, including reports of closed roads and detours and multiple cars stranded with water up to windows. Flooding also forced the evacuation of the David A. Boody School in Brooklyn.

"Drivers are advised to be especially mindful to avoid areas where water covers streets because it is impossible to know how deep the water is or how fast the water is moving," Porter said. "Just 6 inches of swiftly moving water is enough to sweep up a car, and tragically, flooding situations result in many injuries and lives lost every year."

High pressure returning for the first week of October will bring a much-needed reprieve from rain, as sunshine and warm conditions will reign for the new week.

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