Rain is expected to dampen the end of summer’s final weekend on Sunday when a cold front slowly approaching from the west brings with it the possibility of passing showers or a thunderstorm in the afternoon and evening.

Highs will be near 79 degrees, six degrees higher than normal, but clouds will increase throughout Sunday. At night the low will drop to 71 degrees, much higher than the normal low of 56.

“There’s a slow-moving frontal system Sunday off to our west that was to move slowly into our area today [Sunday] and tomorrow [Monday],” said Faye Barthold, a meteorologist with the National Weather Service in Upton. “That’s why there’s a prolonged chance of rain — after that we dry out.”

A wet Monday with lots of clouds starts the workweek with moderate to heavy rain predicted, especially during the morning. Flash flooding is possible. But by midafternoon, the weather will start to improve gradually and highs will reach near 76 degrees.

“There could be one to two inches of rain,” said Matt Hammer, a News 12 Long Island meteorologist. “But we’ll be above average [in temperatures] through Thursday, when fall starts at 10:21 a.m.”

Barthold said Long Island won’t be in the clear from rain until Tuesday.

“The rain will start to move out late in the day on Monday, but there’s still a chance of rain in the overnight hours before it clears out Tuesday morning,” Barthold said.

The sun comes out Tuesday, when there will be mostly bright skies with highs near 80 and lows near 65.

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Mostly sunny skies also are ahead for Wednesday, when highs are forecast near 81 and lows near 62.

Lots of sun is expected again Thursday, with highs near 77 and lows near 61.

A mix of sun and clouds begins the weekend Friday, when highs will be near 78 with lows near 66.