By my math, if that were a single spherical water droplet, it would be almost 3.7 miles in diameter.

If you have trouble visualizing this (as I do), the height of the Empire State Building is 0.2 miles. So imagine a sphere of water 20 times taller than the Empire State Building falling on New York.

Of course, the area and rate it falls on is crucial, but as a way to think about the scale of it I found this useful.

Edit: just saw this was done nicely by the article dreamcompiler linked to!