By Jonathan Allen and Brendan O'Brien
NEW YORK (Reuters) - Torrential downpours after a week of mostly steady rainfall triggered flash flooding in New York City on Friday, disrupting subway service in the country's most populous city and turning many of its streets into small lakes.
A flash flood warning was in effect for New York City until midday as more than 2 inches (5.08 cm) of rain fell in some locations by Friday morning and 2 more inches possible within hours, the National Weather Service said.
"Move to higher ground now. Act quickly to protect your life," the service said in an advisory posted on its website.
The extreme rainfall prompted New York Governor Kathy declared a state of emergency for New York City, Long Island, and the Hudson Valley.
"Please take steps to stay safe and remember to never attempt to travel on flooded roads," she said in a message posted on the X social media platform.
Some 18 million people in the New York metropolitan area and in other major cities along the East Coast were under flood warnings, watches and advisories from the weather service.
Pictures and video footage showed neighborhood streets and subways flooded across New York, disrupting morning traffic for millions of commuters.
Flooding caused major disruptions to the city's subway system and the Metro North commuter rail service, according to the Metropolitan Transportation Agency. Some subway lines were suspended entirely, including the G, which connects Brooklyn and Queens, and many stations were closed.
(Reporting by Brendan O'Brien in Chicago)