Forecast: Showers, thunderstorms possible Monday evening

As expected, temperatures hit the high 80s Monday -- 88 in Islip -- around most of Long Island, with the possibility of showers and thunderstorms still in the picture for Monday evening, forecasters said.

Unsettled weather elsewhere has affected area flight traffic, with average arrival delays of just more than 90 minutes at Kennedy Airport and just over two hours at LaGuardia Airport, according the Federal Aviation Administration website. With some departures from those and Long Island MacArthur Airport affected, the FAA advises travelers to check with their airlines.

An "upper level disturbance" is moving into the area Monday night, said Lauren Nash, a National Weather Service meteorologist based in Upton, with the highest chance of scattered showers and thunderstorms to the north and west of Long Island. The Island faces a 30 percent chance for such scattered precipitation, mostly after 4 p.m., the weather service said.

Earlier in the day the humidity was forecast to remain "uncomfortably high," said Tim Morrin, also a meteorologist in Upton, and the heat index, indeed, hit 91 in Islip and 92 in Montauk, according to Nash.

Long Islanders were still faring a bit better than residents of New York City, where the heat index topped 95 and cooling centers were open all weekend and into Monday for vulnerable residents.

"New York City is typically three to five and even seven degrees higher, especially in Manhattan, which has all those heat sources and not much of a sea breeze," Morrin said.

The forecast calls for the possibility of showers and thunderstorms throughout the week, with the chances growing stronger Thursday and Friday.

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The precipitation later in the week is not related to Tropical Storm Chantal, now moving up the central Atlantic toward Puerto Rico, Morrin said.