A sustained round of torrential downpours after a week of mostly steady rainfall triggered flash flooding in New York on Friday (September 29), disrupting subway service in the most populous US city, inundating basements and turning some streets into small lakes.

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A flash flood warning was in effect for New York until 2:30 p.m. EDT, with as much as 6 inches (15 cm) of rain falling in some locations, including Brooklyn, lower Manhattan and John F. Kennedy International Airport in the borough of Queens, said the National Weather Service.

Across the region, another 2 to 3 inches (5 to 8 cm) could fall before the system pushed out to sea, and some locations could see even more, according to the service’s Weather Prediction Center.

🚨 🌧️ NY Governor Kathy Hochul declared a state of emergency across NYC, Long Island, and the Hudson Valley in response to extreme rainfall and flooding. https://t.co/DsnldtVplZ pic.twitter.com/JQOM8OY73W

— AccuWeather (@accuweather) September 29, 2023

The extreme rainfall prompted New York Governor Kathy Hochul to declare a state of emergency for New York City, Long Island, and the Hudson Valley, and some National Guard troops were deployed to assist in the response.

Flooding caused major disruptions to New York’s subway service and the Metro-North commuter rail service, according to the Metropolitan Transportation Agency, which operates both. Some subway lines were suspended entirely, and many stations were closed.

New York Mayor Eric Adams declared a state of emergency for the city.

Systems producing intense rainfalls such as Friday’s have become more common in many parts of the U.S., including the New York City area.

Global warming has produced more extreme weather patterns in many parts of the world, according to climate scientists.

**🌊NY Flood Emergency!**

NEW YORK: Floods wreak havoc! Gov. Kathy Hochul declares state of emergency for NYC, Long Island & Hudson Valley. Brooklyn bears the brunt with cars submerged & significant damage. Over 4 inches in Central Park alone! Stay tuned for Mayor Adams’… pic.twitter.com/Kd1NvJJdkg

— FlashFactsHub (@FlashFactsHub) September 29, 2023

The rain capped one of New York’s wettest Septembers on record, with 13.74 inches (34.9 cm) of rain falling during the month as of 11 a.m. on Friday, and more on the way, said a forecaster with the weather service’s office in the city. The all-time high was set in September 1882 when 16.82 inches (42.72 cm) of rain fell.

Friday’s deluge followed a bout of heavy downpours and unrelenting winds last weekend from the remnants of Tropical Storm Ophelia. That storm soaked New York City and caused widespread power outages in North Carolina, Virginia, Pennsylvania and New Jersey.

In New York, intermittent rain this week further saturated the ground, setting up conditions conducive to flash flooding.

State of emergency was declared in NYC, Long Island, & Hudson Valley due to extreme flooding. pic.twitter.com/B6rQfYjr6D

— Aldrich (@observer888888) September 29, 2023