What you seeing is the release of steam from the steam utility, which is run by Con Ed. It used to be used widely at one time, but at this point, approximately 7 percent of the city still utilizes this utility in order to power their heating and air conditioning systems. Con Edison produces 30 billion pounds of steam each year through its seven cogeneration plants (which boil water to 1,000°F (538°C)) before pumping it to 100,000 buildings in Manhattan below 96th Street — the biggest steam system in the world.

The enormous explosion that took place on July 18 near Grand Central Station was from the failure of an old underground steam pipe that burst.