Long Island weather: Collision of warm, cold fronts could mean more rain 

The rainy weekend that brought Saturday's showers and thunderstorms could continue into Sunday night with patchy fog early in the day but mostly cloudy and a high near 84 later on, according to the National Weather Service.

All that wet weather can be pinned on what the weather service’s Weather Prediction Center calls a "slow-moving cold front" sweeping into the Northeast and mid-Atlantic from the Lower Great Lakes and Southern Plains, which will collide with "a very warm and humid air mass, sparking numerous thunderstorms."

The showers and thunderstorms are forecast mostly for Sunday afternoon, if they occur.

"Looks not quite as interesting as it's been today," speaking of areas west of the city and Long Island where there was severe weather like flash flooding, weather service meteorologist Dave Radell said Saturday evening. He added: "it's won't feel quite as warm as it's felt the past three or four days."

Radell said weather will be consistent from the Queens-Nassau line out to the East End.

"The next couple days look pretty uniform across the Island. It'll be a little cooler at the beach, the coastal areas," he said.

Earlier, the center said that even the threat of tornadoes could not be ruled out.

"Additionally, a few storms may turn severe between western Connecticut and northeast Maryland with damaging wind gusts and isolated tornadoes possible," the prediction center added, while predicting these threats should end on Sunday when the system reaches the coast.

Much of the Southeast, Lower Mississippi Valley, Southern Plains and the Southwest could also experience a waterlogged weekend, with possible flash flooding and thunderstorms, the weather prediction center said. Yet another heat wave is forecast for the Northern Plains and Northern Great Basin, while California could see dry lightning spark more wildfires.

On Monday, the weather service’s forecast for Long Island has a 30% chance of rain, while thermometers should rise no higher than 81 degrees.

Temperatures during the day from Tuesday to Friday should be capped in the mid- to upper 80s.

A high pressure system, though weak, should reach the region Tuesday, delivering some sunny skies. The air falling in those systems dries and cools, so clouds don’t form.

However, a shortwave — an atmospheric disturbance that pushes the air up ahead of it — "will dig into upstate New York Tuesday afternoon" as a surface trough develops, the weather service said.

The combination means the interior may see showers and thunderstorms. A trough is an elongated area of low pressure. Its warm, rising air can allow vapors to condense.

The odds of rain Wednesday on Long Island are 40%.

And then, the weather service said, "Expect warm and dry conditions Thursday through Saturday, with high temps in the 80s to near 90."

And with lower humidity, it added, "expect heat index values to remain close to actual temps."

Those heat indexes, by measuring both heat and humidity, reveal just how hot it may feel.

By next Saturday, it's forecast to be mostly sunny, with a high of 83 degrees, according to the weather service.