Frigid Arctic air is plunging southward across much of the eastern United States through Valentine's Day weekend, leading to dangerously cold temperatures in cities from Boston to Pittsburg.
Following a month so far with temperatures averaging 5 to 10 degrees Fahrenheit above normal, this weekend’s projected temperatures will be among the coldest of the winter.
A polar vortex is expected to bring single-digit and sub-zero temperatures in New England and down into the central Appalachians. The coldest conditions are expected late Saturday into early Sunday across portions of the Ohio Valley, the Mid-Atlantic, and the Northeast.
“High temperatures in the I-95 mid-Atlantic corridor will struggle to reach the lower 20s by Sunday and may not reach 10 over the interior," said AccuWeather Meteorologist Edward Vallee.
The so-called polar vortex is a low pressure system that is typically centered near the North Pole and tends to keep the coldest air trapped in northern Canada. But occasionally it weakens or shifts enough to allow frigid air to head southward into the US.
The National Weather Service reports that the cold air could combine to make it feel like it's 20 to 30 degrees below zero in parts of the East, making it dangerous for those spending time outdoors without proper dress. The conditions have the potential to cause frostbite and hypothermia, freeze pipes, and harm pets.
Officials across the region have warned people to take precautions when going outside. The city of Pittsburgh is opening warming centers at 24 parks and recreation facilities for those who don't have other ways to stay out of the cold.
Temperatures are also expected to drop in the upper Midwest on Friday because of a frigid air mass, while a Pacific system will affect the Northwest.
In western Michigan, meteorologists warn that a looming winter storm could produce whiteout conditions. Six to 10 inches of snow is predicted by the time the storm ends on Saturday.
Lake effect snow will develop south of Lake Ontario and Lake Erie, falling in northeast Ohio, northwest Pennsylvania, and areas of New York. The District of Columbia is also expecting up to half an inch of snow Friday night.
This report includes material from The Associated Press.