The past has caught up with the National Weather Service — at least two decades’ worth.

An added 20 years of climate data for Long Island MacArthur Airport have been recovered, verified and added into the mix, so official readings now date back to Sept. 5, 1963, instead of the previous Jan. 1, 1984, National Weather Service staffers say.

What had been the hottest day for the earlier record-keeping period — July 5, 1999, with its 102 degrees — has been dislodged by the 104 recorded on July 3, 1966, according to the Northeast Regional Climate Center, based at Cornell University.

The coldest days, ones that saw minus 14 degrees and minus 8 degrees, occurred respectively in February 1967 and January 1965 — bumping January days in 1984 and 1988 to third and fourth place on the top 10 coldest days list.

Climatologists can now “see a bigger picture,” said Chris Stachelski, regional observation program leader at the National Weather Service’s Eastern Region Headquarters in Bohemia. The more years of data the better, he said, when looking to study climate trends and variations.

Compared with the longer records for locations such as Central Park, the added 20 years doesn’t seem like a big deal, but “it will still help increase our understanding of Long Island weather,” said Bill Korbel, News 12 Long Island meteorologist.

advertisement | advertise on newsday

The added data provide a fuller view locally of what has been occurring regionwide: a more recent trend toward warmer, wetter conditions.

“The Northeast as a whole is seeing an increase in temperatures and is becoming slightly wetter,” said Jessica Spaccio, climatologist with the regional center.

Overall, MacArthur’s revised top 10 lists for coolest days and months are now populated primarily by data from the earlier years — the ’60s through the early ’80s — while more recent years dominate the records for warmest weather.

Last year, Stachelski came across the data in the service’s internal archives — scanned images of handwritten, daily reports offering hour-by-hour temperatures, visibility, wind speeds and direction, as well as precipitation.

A Newsday carrier delivers the paper through the snow in late 1960. Photo Credit: Newsday

It made sense to add key elements of the data to MacArthur’s official records, he said, because the airport is an especially valuable location, weather-wise.

MacArthur’s conditions are “fairly representative” of the bulk of the Island — thanks to its location at about midpoint in Ronkonkoma — apart from more extreme readings found toward the Island’s west and east, Stachelski said.

And despite the area’s suburban development through the years, it remains “more of a natural setting,” with trees and grasses, Stachelski said. That’s an advantage over airports in more urbanized areas, where heat from “tons of pavement” can somewhat mask the genuine climate conditions, he added.

The airport was named an official weather service climate site in 1984, meaning its information is used for record-keeping and climatological purposes, said Tim Morrin, weather service meteorologist in Upton.

But data had been being collected decades before that by Federal Aviation Administration staff. Now weather observations there are recorded by an automated computer system, which is monitored by contract weather observers on site.

A Newsday carrier delivers the paper through the snow in late 1960. Photo Credit: Newsday / John Paraskevas

As a Long Island native, Jeff Tongue, science and operations officer at the weather service’s Upton office, said it was gratifying to have some holes in the data officially filled in for memorable weather events, including a major blizzard in February 1978.

advertisement | advertise on newsday

Why the information wasn’t incorporated into the system in the early days was somewhat of a mystery, he said. The office over the years made informal inquiries as to the status of the data they knew existed.

Processing two decades’ worth of daily observations was certainly labor-intensive, Stachelski said. He and several colleagues keyed the measurements into a spreadsheet, which fed a searchable database. Then the real fun began: various layers of quality control and verification.

As of March 18, the button was pushed, adding decades of data to the service’s official history for Long Island weather.

“We were just giddy of the fact we have more longevity of data we can work with,” Morrin said.