Late-season cold snap cools LI Summer

Oh, what a difference a little late-summer cold snap can make.

The three months -- June, July and August -- that make up the meteorological summer of 2020 were the second-hottest since 2010. But the astronomical summer that ended Tuesday morning was only the sixth-warmest, according to the National Weather Service’s Islip office, whose records began in 1963.

What a difference just a few tenths of a degree can make when it comes to busting records.

The average temperature for the June 20 to September 22 astronomical summer (based on the Earth's rotational axis) was 74.3 degrees, calculated Tim Morrin, an NWS meteorologist.

That was three-tenths of a degree cooler than the average of 74.6 for the trio of months meteorologists call summer.

"The last four days were cooler than average — and yesterday was 10 degrees cooler," Morrin said by telephone. The chill came courtesy of Canada, which sent the jet stream as far south as the Tennessee Valley and the Carolinas, cooling New York along the way, Morrin explained.

Islip’s temperature fell to 38 degrees on Monday night, Morrin noted, with thermometers falling to the 40s in other spots. That Islip reading is as cold a night as Long Island has had in September, the historical records show, a low hit just five times since 1963.

September’s mean temperature is 65.6 degrees; the maximum is 73.8 and the chilliest is 57.5, according to the NWS records.

And despite the intense though brief rainstorm that flooded dozens of roads earlier this month, Long Island and the rest of the state were still in a moderate drought as of Sept. 15, according to the U.S. Drought Monitor, a federal-private program.

The average amount of precipitation in September is 3.58 inches, the NWS says.