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 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 of snowfall in Boston.

However, some Mainers not only were dealing with bitterly cold temperatures but also were digging out after a Saturday winter storm that dumped more than a foot of snow on coastal islands, according to a statement issued Sunday by the National Weather Service.

The highest total — at 25 inches — was recorded on Matinicus Island. Vinalhaven had 22 inches, North Haven had 18 inches and Isle au Haut had 13 inches.

While the storm did not pan out as predicted in many places, other Knox County locations that saw half a foot or more of snow, including Rockport at 9 inches, Camden with more than 8 inches, and Thomaston, Union and Hope, all of which which had 6 or more inches of new snow.

A wind chill advisory remained in effect through Sunday night for parts of Aroostook, Piscataquis, Somerset, Oxford and Franklin counties.

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

In Cambridge, Massachusetts, Kristen Carlson, 25, and her boyfriend Ross Crory, also 25, were adapting their plans.

“We’re going to brunch,” Carlson said. “We’re going rock climbing later. Indoor activities. Tonight we’re staying in and cooking dinner.”

Others embraced the extremes, with more than 2,000 taking part in the Sea Isle, New Jersey, annual “Polar Bear Plunge,” dipping into the icy Atlantic to raise funds for the city’s revitalization.

Police throughout the region sought homeless people to urge them to spend the night in shelters, where cots, mats and even chairs were rolled out to give people a place to shelter from the cold.

But Kevin Taylor, a 49-year-old native of Massachusetts living on the street in Harvard Square, said he had coped with the cold on his own.

“I got a sleeping bag sized tent that protects me from wind and snow. I got a zero degree sleeping bag and fleece blankets,” Taylor said. “I was born and raised in New England. I’m used to this. It’ll start breaking tomorrow.”

Forecasters said temperatures around Boston would rise to about 29 degrees Fahrenheit on Monday.

High temperatures for Maine on Monday are expected to be in the teens and 20s.

BDN writer Dawn Gagnon contributed to this report.