Airlines canceled nearly 3,000 flights, winter storm warnings stretched from Maine to Maryland and salt trucks deployed across the region Thursday as the season’s most dangerous snow event rolled into the Northeast.

National Weather Service winter storm warnings and watches covered more than 40 million people. Parts of central Pennsylvania had already picked up eight inches early Thursday, with northern Jersey hit with up to five inches. Albany, N.Y., recorded four inches of snow in one hour.

Much of the region enjoyed seasonally warm temperatures in the 60s and 70s Wednesday. By Thursday morning, heavy snow snarled the morning rush in New York.

Dangerous travel conditions were forecast for I-95 cities from Philadelphia to New York City and Boston, the National Weather Service said. Scores of school districts, including Boston and New York City, shut down.

More than 1,700 flights in New York-area airports alone were canceled. The city rolled out 2,300 salt spreaders and plows, and de Blasio advised residents to use public transportation if they must travel at all.

In New Jersey, a jackknifed tractor trailer closed all eastbound lanes of I-78 near Bedminster, about 45 miles west of New York City. The New Jersey Turnpike speed limit was lowered to 35 mph for its entire 125-mile length.