Unseasonably warm weather predicted this week on Long Island

A cloudy but calm Columbus Day is likely to be followed by several days of unseasonably warm conditions, the National Weather Service said Monday.

The service's Upton office said there's a slight chance of showers later Monday, into the evening hours, and again on Wednesday night. But most of the week calls for temperatures in the low to mid 70s, with cooler daily highs expected by the weekend.

The warmer-than-normal temperatures -- with partly sunny skies -- are because of a lingering high-pressure system just offshore and slow incoming low pressure from the west, the service said.

"We have a good southerly flow because of a combination of offshore high pressure and an area of low pressure to the west," said Brian Ciemnecki, a meteorologist with the Upton office. "That southerly flow taps into warm Gulf air."

Ciemnecki said the cooler air will develop later in the week, probably as early as Thursday night.

As high pressure lingers offshore, clouds persist and the chance of rain is about 20 percent for both nighttime hours on Monday and again on Wednesday, the service said.

By Thursday night, the chance of rain increases to 60 percent.

Temperatures are expected to drop gradually, with daily highs for the weekend most likely in the upper 60s.