Scientists and meteorologists say one possible reason for such a sharp temperature drop was that the kink in the winds came later in the winter this year than in some previous years.

“It does so over Canada all the time,” said Thomas Herrington, a professor of ocean engineering at Stevens Institute of Technology. “To come this far south, it usually takes a push from another system, usually a warmer air system over Alaska or Greenland.”

The kink created a trough of cold, dry air in the Plains and Midwest. At the same time, outside the trough, warm moist air was brought up from the south. As the kink traveled eastward across the country, the warm air was quickly replaced by the cold, and the mercury fell, sometimes startlingly fast.

“It just so happens that the air this time has managed to grow unusually cold,” said Jeff Masters, director of meteorology with the website Weather Underground.

Weather Underground’s historian, Christopher C. Burt, said temperature drops like the one forecast for New York were not unprecedented. “You go back 100 years, and you’ll see a lot of times when this has happened,” he said.

Drops tend to be more rapid and extreme in the Midwest and Plains than on the East Coast. In the nation’s midsection, there is little to stop the onrushing Arctic air, and the Rocky Mountains tend to hem the cold air in.

This can create a “Blue Norther,” a temperature drop of dozens of degrees in a few hours. On Nov. 11, 1911, in Oklahoma City, for instance, the temperature plummeted from 83 degrees in the afternoon to 17 at midnight.