Long Islanders will see things start to cool down this week to signal the arrival of fall on Wednesday.

Temperatures on Sunday will be the most summerlike of the week; it will be mostly sunny with highs reaching around 80 across the island. High humidity will also make for a sticky morning but lows at night will dip into the mid-50s for most areas.

"The morning will feel a little on the humid side and the lows at night in the Pine Barrens could drop to the lower 40s," said Faye Barthold, a meteorologist with the National Weather Service at Upton. "But a cold front will be coming from the west through New York City so by this afternoon it will be less humid."

Cooler weather starts on Monday for the start of the workweek and the start of a week of sunny days.

Highs will be in the lower 70s and lows will be in the mid-50s -- with days in the lower 70s, or about average for this time of year. Barthold said temperatures average from 72 to 73 degrees in Islip.

Tuesday will see more highs in the lower 70s and lows in the mid-50s. Nighttime lows will be in the mid-50s.

On both Wednesday and Thursday highs will be in the mid-70s and lows will be in the upper 50s.

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Daytime temperatures drop slightly for the beginning of the weekend on Friday when highs will be in the lower 70s and nighttime lows will be in the mid-50s.