Why is New York flooded?

America's National Weather Service has issued its first ever flash flood warning for New York City as rain clogs the Big Apple's subway lines and streets in Manhattan, Brooklyn and New Jersey.

The alert level is normally reserved for "exceedingly rare situations when a severe threat to human life and catastrophic damage from a flash flood is happening or will happen soon".

Bill de Blasio, Mayor of New York City, said: "We’re enduring an historic weather event with record-breaking rain across the city, brutal flooding and dangerous conditions on our roads."

Read more: Where do storms get their names and who chooses them?

Almost 8cm of rain fell on Central Park, rapidly overwhelming the city's infrastructure.

The damage to New York was caused by the remnants of Hurricane Ida, that made landfall 1,380 miles away in Louisiana.

Ida has been recorded as the second most intense hurricane to ever hit the state, behind Hurricane Katrina in 2005.

Winds of up to 172mph battered Louisiana, damaging surrounding states and sending it north-eastwards to New York.

After passing the Cayman Islands and Western Cuba, the then 'Storm Ida' underwent a period of 'rapid intensification', with winds of 40mph more than doubling quickly.

Ida was formed in the Caribbean Sea and was whisked into the fifth most intense hurricane the US mainland had ever seen in the Gulf of Mexico. A result of warm summer temperatures and moist air, the Gulf is a breeding ground for deadly storms.

As the hurricane hurtled towards the northeast, it became multiple tornadoes - widening its reach and destruction.

Ida has left millions without power and caused a death toll in double figures that is expected to rise.