Plunging temperatures and high winds rocked most of the Northeast including New York state on Wednesday. A cold front and arctic air roared into New York before dawn, sending Tuesday’s almost springlike temperatures plummeting. Buffalo went from 53 degrees at 3 a.m. Wednesday to 15 degrees by noon. Classes were canceled at most area schools. High winds were suspected of collapsing a scaffold at a Brooklyn building that killed a construction worker and seriously injured another Wednesday morning. The National Weather Service in Buffalo reported sustained winds of 40 to 50 mph, with a peak gust of 68 mph around 10:30 a.m. Across the state, peaks of 46 mph were reported at LaGuardia Airport and close to 50 mph at Kennedy Airport.