The urban flood threat prompted New York City officials to issue a travel advisory starting at 4 a.m. Friday through 6 a.m. ET Saturday.
The urban flood threat prompted New York City officials to issue a travel advisory starting at 4 a.m. Friday through 6 a.m. ET Saturday.
CNN  — 

A coastal storm is expected to drop a prolific amount of rain over millions in New York City and the Northeast Friday, with rainfall intense enough to flood subways and roads.

Many places in the region began seeing rain Thursday night, but the heaviest rainfall is set to begin Friday.

The flood threat is impacting around 25 million people across the Northeast, and the New York tri-state area is facing a Level 3 of 4 “moderate” risk for flash flooding, the National Weather Service warned.

Intense rainfall rates of 1 to 2 inches an hour – with isolated rates of more than 2 inches per hour – are possible, bringing the threat of a dangerous morning commute for many as the rain could cause serious flash flooding on roads and even in subway stations.

The urban flood threat prompted officials in New York City to issue a travel advisory starting at 4 a.m. Friday through 6 a.m. ET Saturday, warning of potentially “widespread travel impacts” during the morning commute.

“We urge New Yorkers to prepare for heavy rain and potential flooding throughout Friday and Saturday morning,” NYC Emergency Management Commissioner Zach Iscol said. “All New Yorkers need to exercise caution. If you must travel, consider using public transportation and allow for extra travel time, and if you must drive, do not enter flooded roadways.”

The city’s Metropolitan Transportation Authority urged passengers to use caution while traveling.

“We’re expecting heavy rain and possible flooding tonight and tomorrow, with especially heavy rainfall during the AM rush hour,” the MTA said in a post on X. “Give yourself extra time to travel.” Service statuses are updated on MTA’s website.

Even an inch of rain could cause flooding in some parts of the region that are still saturated from last weekend’s storm.

Central New Jersey northward to Manhattan, Long Island in New York and into southern Connecticut and the Hudson Valley are expected to see the highest amounts of rain.

Meanwhile, neighboring cities of Philadelphia and Boston could too up to 2 inches of rain while Hartford could collect up to 3 inches or more. Overall, widespread rainfall totals between 2 and 4 inches are expected, but those totals could increase to between 5 and 8 inches in some areas.

The potential flood threat can be especially dangerous for cities like New York, where basement flooding caused by Hurricane Ida’s remnants in 2021 proved deadly.

New York City subways to remain operational

Ahead of the expected heavy rainfall, the MTA plans to keep all services at its more than 470 stations running Friday.

“There may be impacts to service, but our plan is to run service everywhere the MTA operates,” MTA Chair and CEO Janno Lieber said during a news conference Thursday, acknowledging that water will inevitably creep into some facilities.

The MTA has installed drain covers, Lieber said, and will be deploying pump trains and sending crews to strategic locations throughout the transit system.

The public transit network has also prepared additional buses on standby to provide supplemental service in case the rail system is hindered by the storm, Lieber added.

The heaviest rainfall in the greater New York City area is expected to persist through Friday, ending Saturday morning.

The flooding impacts may also be exacerbated by the final supermoon of this year, which will occur Friday morning. The event typically creates more extreme tidal cycles that could increase the flood risk along the East Coast.

In anticipation of that, coastal flood advisories extend more than 300 miles from Bridgeport, Connecticut, through Virginia Beach.

Up to a foot of inundation above ground level is expected in low-lying areas near shorelines and tidal waterways, according to the National Weather Service.

CNN’s Eric Zerkel, Robert Shackelford and Nicki Brown contributed to this report.