Long Island is in for a rainy week, with a flash flood watch forecast for parts of Monday and Tuesday in Nassau County, according to the National Weather Service.

Forecasters are predicting an 80 to 90 percent chance of showers and thunderstorms that are “strong to severe” starting Monday afternoon as a cold front moves through the area, said weather service meteorologist Joe Pollina in Upton. Temperatures will be in the upper 70s Islandwide but cooler along the coast.

The rainfall is expected to be between three-quarters of an inch on the East End and 2 1⁄2 inches in northwestern Nassau County by the time it ends around midnight Tuesday. “Damaging winds” also are forecast.

The flash flood watch is in effect from noon Monday to 4 a.m. Tuesday, Pollina said.

Scattered thunderstorms could bring wind gusts up to 60 mph with large hail up to an inch, according to a National Oceanic and Atmospheric Administration briefing released Sunday afternoon. A weak tornado is possible and the weather is expected to be at its worst between Monday afternoon and Monday evening, the briefing said.

The likelihood of rain will decrease throughout the day on Tuesday and by Tuesday night, “We are completely dried out,” Pollina said, with temperatures in the upper 70s to mid-80s.

Things really brighten up for Wednesday, when it will be mostly sunny with a high of 80 and low of 64.

“It should be dry Wednesday, Thursday and Friday, with the next chance of precipitation not until Friday night,” meteorologist Pat Maloit said.

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Look for mostly sunny skies on Thursday, when the high will be 81 and the low 66.

Mostly sunny skies return for Friday, but there’s a chance of a thunderstorm. A high of 83 degrees is expected and a low of 68 degrees.

With Lisa Irizarry