A flood advisory that had been in effect for southern Nassau County until 8 p.m. Wednesday was canceled as of 6:44 p.m., according to the National Weather Service.

At about 6 p.m., radar had indicated heavy rain, "with rainfall rates of 2 inches per hour . . . capable of causing minor flooding," the weather service said in its earlier advisory.

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By around 5 p.m., moderate to occasionally heavy showers were moving across northern and central Nassau, and spreading into northwest Suffolk, said Joe Pollina, National Weather Service meteorologist based in Upton.

See alsoCurrent conditions

Late Wednesday afternoon, thunderstorm activity was leading to average arrival delays of two hours at Kennedy Airport, with some departures held up for up to an hour and a half, according to the Federal Aviation Administration. LaGuardia was seeing some arrival delays averaging around half an hour, with departures held up for as long as two hours, said the FAA, which advised travelers to check with their airlines.

With humid conditions, the already moist air could contribute to locally heavy downpours, said Nelson Vaz, weather service meteorologist based in Upton. Some spots on Long Island could see very little rain, while other places may possibly get more than an inch.

Though the air temperature reached 87 degrees at Long Island MacArthur Airport, the "feels like" temperature was 93 at around 4 p.m., thanks to a dew point of 71.