Thursday's forecast calls for daily highs in the low 70s across Long Island, almost 10 degrees above normal for this time of year.
The National Weather Service's Upton office said the warmer than normal conditions will be pushed out starting Friday by an incoming cold-air mass from the Great Lakes.
News 12 Long Island meteorologist Bruce Avery said most parts of Nassau and Suffolk counties should get close to or above 70 degrees on Thursday, threatening the daily record high of 73 degrees set in 1990.
"Thursday will feature a mix of sun and clouds with breezy and warm conditions," Avery said.
Winds from the southwest will blow from 5 to 15 mph.
Avery said there's also a chance for an early shower Thursday night, followed by clearing skies with an overnight low of 49.
While Friday's drop in temperature will be noticeable -- daily highs in the upper 50s are expected -- conditions will remain dry and mostly sunny.
Avery said the weekend looks OK, with Saturday being mostly sunny with highs about 60 degrees.
Clouds move in Sunday, with a slight chance of sprinkles, Avery said. Daily highs in the low 60s are likely.