NYC Monthly Summary: September 2015

Summer-like weather extended well into September in New York City this year. With an average temperature of 74.6°F, it was the city’s warmest September on record! It surpassed the previous record set in 1961 by 1.1°F.

Overall, we had twenty-seven out of thirty days with high temperatures above average. Six of those days posted readings in the 90s, including September 8th when the mercury soared to 97°F in Central Park, marking a new record high for the date. Typically, we only see one 90-degree day during September in NYC. Historically, our average temperature for the month is 68°F.

This extended period of warmth was produced by a persistent ridge in the jet stream over the eastern US. It allowed warm air from the south to flow further north than it normally would at this time of year.

In terms of precipitation, September was unusually dry and marked the third consecutive month that NYC received below average rainfall.  In all, we received 3.28 inches of rain, which is one inch below normal. The vast majority of this modest total fell on two separate days in the form of intense downpours. In fact, September 10th set a new daily rainfall record with 1.58 inches measured in Central Park. Nonetheless, despite these soakers, NYC remains in a moderate drought according the latest report (9/29) from the US Drought Monitor.