Long Island weather: Sunny, warm spring day

Saturday should offer all the delights of spring: sunshine, a daytime high of 70 degrees, and breezes topping out at 15 mph, the forecasters said.

That all changes after midnight, when a high pressure system moves offshore and storms sweep in from the Plains, according to the Weather Prediction Center, which is part of the National Weather Service.

On Long Island, the weather service said, "Clouds lower and thicken tonight, with rain quickly overspreading the area after midnight as the approaching low moves off the Mid-Atlantic coast."

At least the mid-Atlantic is not at risk of the possible large hail, thunderstorms and even tornadoes the prediction center says that same system could bring to the Southeast and the central Gulf coast.

While Sunday’s showers on Long Island could be heavy at times, the weather service said, they should mostly clear out by the early afternoon.

Look for as much as three-quarters of an inch of rain and a daytime high of 59 degrees.

And then Islanders can expect a mid-week warming trend, combined with a high pressure system that should result in at least partly clear skies from Monday to Thursday, the weather service said.

Monday and Tuesday will see thermometers reach the low 60s during the day.

While the night time low on Monday will be a chilly 42 degrees, thermometers should hover in the 50s during the rest of the week nights.

The warming trend will be brief but noticeable.

"Temperatures Wednesday and Thursday still are on track to be 10 to nearly 15 degrees above seasonal levels, mainly inland away from the marine influence in a southerly flow," the weather service said.

That means a daytime high of 73 degrees on Wednesday, the warmest day of the week, it said. Daytime highs in the upper 60s are forecast for Thursday and Friday.

"Temperatures will be more normal by the weekend behind the frontal system," the weather service said, referring to an arriving low pressure system.