A dangerously frigid blast of arctic air brought the coldest weather of the winter to Maine on Wednesday night, prompting forecasters at the National Weather Service in Gray to advise people to stay indoors if possible.

Temperatures in Portland had dropped to 4 degrees by 10:30 p.m., and with the wind chill it felt like it was 14 degrees below zero. The weather service was predicting that temperatures in Portland would drop to 8 degrees below zero around sunrise Thursday. The city’s record for the day is 16 degrees below zero, set in 1942.

The weather service said winds out of the northwest at 10 to 20 mph, with gusts up to 30 mph, were expected to send the wind chill to 45 below zero over northern parts of the state and 30 below near the coast.

The forecasters in Gray were urging people to dress in layers and cover their faces if they have to go to outdoors Thursday.

“It’s really dangerous to be outside,” said Stacie Hanes, a meteorologist with the weather service. “Stay inside if you can and keep your pets inside. You don’t want to be outside and have exposed skin. Any kind of prolonged exposure in such strong winds could lead to death.”

The subzero wind chills were expected to last through Thursday evening before the temperature reaches a predicted high of 29 degrees Friday.

Hanes, the weather service forecaster, said the temperature on Mount Washington on Wednesday night was 33 degrees below zero, and the wind chill made it feel like it was 78 degrees below.

In Portland, police Lt. Robert Ridge said officers were keeping an eye out for anyone wandering the streets who might need shelter.

The extreme cold prompted officials in Boston and Providence, Rhode Island, to close schools Thursday, according to The Associated Press. Elsewhere in Massachusetts, Worcester and Springfield also were closing schools.

The icy temperatures were posing a particularly difficult situation for people who are homeless or at risk of becoming homeless.

All 48 beds at the Mid-Maine Homeless Shelter in Waterville were full Wednesday and people were sleeping on mats on the floor, said Betty Palmer, the shelter’s executive director. Twenty-six children were living there Wednesday.

Linda Fossa, Waterville’s health and welfare director, said her office is seeing an increase in the number of people worried they will become homeless and those concerned about not having enough heat in their homes.

“We’ve noticed it with the phone calls and the foot traffic,” Fossa said.

People who are homeless, in transition or living in places that are not warm enough, flock during the day to businesses and other places that have heat.

The Waterville Public Library was one such haven Wednesday.

“Overall usage is up, and there are no limits to how long people can stay here,” library Director Sarah Sugden said. “It’s great to have this place available for people who need it. It’s been great for families, especially, because they can come in and do something in the warmth that is child-friendly and offers a variety of activities to do that are free.

“We don’t ask people to identify why they’re here, and we never would. We can assume that our visitors appreciate that our heat’s on. Everyone’s welcome and always will be.”

At the Sacred Heart Soup Kitchen on Pleasant Street, director Richard Willette Sr. said that when it’s cold outside, more people tend to come in for lunch.

He said between 108 and 125 people eat at the kitchen daily. He estimates that 80 percent really need the meal and the rest may be lonely, want a meal and seek companionship.

Homeless people suffer a lot, he said.

“They go and they get a box and cut the end of it off and sleep in it,” Willette said. “And they come in here to warm up.

Willette, 81, has directed the soup kitchen for 35 years.

“It’s a long day for them,” he said. “Cold makes it worse.”

Morning Sentinel Staff Writer Amy Calder contributed to this report.