Cold air swinging south from Canada left residents from North Dakota to New York contending with severe weather that proved deadly in some areas.
"Those people who work outside have to be careful," CNN meteorologist Chad Myers said Wednesday.
Authorities say exposure to sub-freezing temperatures left at least three people dead in Wisconsin, Minnesota and Illinois.
The coldest air so far is in northwestern Quebec, where temperatures plummeted to 45 degrees below zero Fahrenheit in the city of Rouyn, according to forecasters.
"We feel the wind chill, and so do pets. You need to find some place indoors and out of the wind for them," Myers said.
In the northern Maine town of Presque Isle, temperatures hung around 24 below. And in Grand Forks, North Dakota, residents bundled up to stave off a potentially deadly wind chill that hovered even lower -- around 33 below.
"The biggest thing is staying out of the wind. That's what kills you," said Michael Lannen, who works at a Menards hardware store in Grand Forks.
"It seems we get one of these kinds of weeks every year, so everyone is just trying to bundle up and stay indoors."
In Ohio, the State Highway Patrol closed Interstate 90 in Lake County near Cleveland after white-out conditions contributed to accidents in the area.
Forecasters also predicted possible ice accumulations Thursday into Friday, leaving areas as far south as Georgia under a winter weather watch.
CNN iReporters sought to demonstrate the effects of the weather by tossing boiling water into the air and watching as the mist particles froze midair.
In New York and New Jersey, homes destroyed by Superstorm Sandy in places such as New Dorp, Staten Island, and Far Rockaway, Queens, still lack basic utilities needed to restore heat.
But the cold weather may have been good news for those who sell hot coffee.
"On days like this, coffee sells. Bagels don't," said Sami Akramia, a 41-year-old food cart worker bundled up in Midtown Manhattan as the temperature dropped to 4 degrees.
National Weather Service forecasters say they expect the cold weather to last throughout the week.