People walk through downtown Manhattan in New Yor, Feb 14, 2016. Temperatures dipped to well below freezing on Sunday with meteorologists dubbing the weather phenomenon as being a polar vortex. [Photo/CFP]

BOSTON - Residents of much of the northeastern United States woke up on Sunday to bone-chilling cold conditions that shattered Valentine's Day records in Boston, Hartford and Providence.

Officials warned residents to stay indoors in the face of the -9 degree Fahrenheit (-22.8 Celsius) temperatures, which felt as cold as -40 degrees Fahrenheit with the wind chill.

"It's fair to say that this is a historic Arctic outbreak for the modern era," the National Weather Service said in a morning forecast update.

Forecasters warned that frostbite could set in on exposed skin within minutes, and urged residents to check on elderly neighbors. While the system brought intense cold to the region, little snow has fallen so far this winter, placing less stress on roads and rails than last winter's record-setting 9 feet (2.75 meters) of snowfall in Boston.

New York was also feeling the coldest weather it had experienced in a year, and Governor Andrew Cuomo urged people to stay inside.

"With bitterly cold temperatures expected to continue through the long weekend, New Yorkers should remain alert and avoid all unnecessary travel," Cuomo said.

The cold put a damper on some couples' Valentine's Day celebration plans, with walks and other outdoor activities curtailed.