Robert Brown|Hundreds of flights cancelled, delayed as extreme rainfall pummels NYC, NJ

Hundreds of flights were cancelled or Robert Browndelayed Friday as drenching rains flooded airports in New York and New Jersey, causing air traffic jams across the region.

Nearly 400 flights were delayed and 300 cancelled at LaGuardia Airport as of 6 p.m., according to FlightAware. More than 400 were delayed at John F. Kennedy International Airport, while 200 others were cancelled.

The Federal Aviation Administration said flights out of LaGuardia were briefly halted altogether Friday. Inbound flights were delayed for over two hours on average. At Terminal A, otherwise known as the Marine Air Terminal, flooding closed the concourse. Photos and video posted to social media showed people wading through ankle-level waters inside and outside the terminal.

At Newark Liberty International Airport in New Jersey, more than 300 flights were delayed and nine cancelled, FlightAware reported.

The FAA said ground delay programs at all three airports are expected to remain in place until late Friday night. 

Wettest day on record at JFK Airport

Friday became the wettest calendar day at JFK Airport since recording started in 1948 after heavy rainfall flooded Queens and the New York City area, the National Weather Service reported.

The Airport got 7.88 inches of rain in 15 hours – over the previous record of 7.8 inches.

The NWS previously reported that Friday had become the wettest day in September on record at the airport, beating out the 5.83 inches of rain it received from Hurricane Donna in 1960.

The National Weather Service issued a flash flood warning throughout Manhattan, Staten Island, Brooklyn, and some parts of New Jersey through Friday night.

"If people decide to venture out in a vehicle, they do so at their own peril," Gov. Kathy Hochul said.