Steam rises from Boston Harbor as
© Joseph Prezioso
Steam rises from Boston Harbor as temperatures reach -7F (-14C) in Massachusetts, on 4 February.
An Arctic blast has swept through numerous parts of the north-east, leaving millions of people under wind chill warnings and cities and states issuing emergency warnings.

Record-breaking temperatures will be 10 to 30 degrees below average over parts of the north-east and into the coastal mid-Atlantic, the National Weather Service announced on Saturday, with wind gusts potentially reaching up to 40 to 55mph (64 to 88km/h).

The wind chills from the blast have the potential to be once-in-a-generation cold, the agency added.

The cold, which is expected to last throughout the weekend, has prompted officials across multiple states to issue emergency orders and warnings that urge residents to remain indoors.

In Boston, the mayor, Michelle Wu, declared a cold emergency for Friday through Sunday as the city is expected to experience wind chills below zero degrees Fahrenheit over the weekend.

"I urge all Boston residents to take precautions, stay warm and safe, and check on your neighbors during this cold emergency," Wu said in a statement.

The city has activated warming centers at community sites as Boston police conduct wellness checks among residents while handing out gloves, hats, jackets and hand warmers.

In Southwick, Massachusetts, the arctic blast has been blamed for the death of an infant who was struck alongside a 23-year-old woman in a vehicle by a falling tree branch.

In New Hampshire, the governor, Chris Sununu, has urged residents to prepare for the severe cold and "potentially life-threatening" weather.

"During this dangerous cold spell, it's important for [residents] to plan ahead and stay indoors as much as possible. Remember to check on relatives, neighbors, the elderly and pets," Sununu warned as emergency shelters across the state are made available to homeless people.

Sununu's office also warned that frostbite is possible within 15 minutes when wind chill values are near -25F (-31C). At -30F, hypothermia can occur in about 10 minutes.

New York's governor, Kathy Hochul, issued a warning Thursday to New Yorkers urging them to exercise caution when using space heaters.

"New Yorkers across the state will experience dangerously cold temperatures and life-threatening wind chills this weekend," she said. Now is the time to prepare: plan to limit your time outdoors this weekend and know where to take shelter. Take all necessary precautions to ensure your residence is safely heated and use caution if you plan to use an alternative heat source, such as a space heater."

Frostbite safety tips listed on the governor's website include refraining from rubbing or massaging cold body parts when frostbitten until indoors, drinking warm liquids and removing rings, watches and anything tight.

Residents have also been warned to not approach a hot stove or heater or use a heating pad, hot-water bottle or hairdryer as that can result in burns before feeling returns.

In New York City, what is known as a code blue weather emergency has been in effect as of Friday. That type of notice is issued when the temperature drops to 32F or less between 4pm and 8am, according to the National Weather Service.

"During #CodeBlue, shelter is available system-wide for anyone brought to a shelter by outreach teams," the city's department of homeless services said in a tweet on Saturday. "Accommodations are also available for walk-ins."