While Monday night's storm enraptured the Instagramming masses with pink lightning, hail, and rainbows, the more discerning urban explorers headed underground, where subway platforms were transformed into a tropical rain forest—humid with human sweat and cooled, in places, by cascading flood waters.

Like the R train platform at Jay Street in Brooklyn, as captured by tipster Mark C. Plug in your headphones, close your eyes, and it's almost meditative...

An underground waterfall

A video posted by Pamela Soto (@pamalamelaa) on

Back above ground, New Yorkers frolicked like schoolchildren in a summer sun shower.

And the LIRR was not spared, nor was this abandoned crust of pizza.

Yesterday’s subterranean waterworks may not have surpassed the extremes of last summer’s day of reckoning, but it’s early in the season yet!