Millions of Americans across the Northeast should brace for what could be the coldest temperatures in over a decade this Valentine's Day weekend, forecasters warned Friday.
The National Weather Service said the "life threatening" icy blast was set to arrive in the region Saturday, but the coldest air would not arrive until Sunday morning — with several cities facing the prospect of subzero temperatures.
Boston's forecast low of 2 below zero looked relatively balmy compared to the outlook for minus 9 in Hartford, Connecticut. Albany was forecast to experience minus 10, with minus 11 possible in Worcester, Massachusetts, according to The Weather Channel.
While it's not expected to see subzero temperatures, New York City won't escape the chill with a bitter forecast for 2 degrees on Saturday.
"For people stepping outside on Sunday morning, it's going to be like walking into a freezer," said Weather Channel Lead Forecaster Michael Palmer. "This will be the coldest air for more than a decade for much of the Northeast."
Wind chills are expected to plummet 20 to 40 degrees below zero across the region, with the National Weather Service issuing a patchwork of wind-chill warnings and watches. It said conditions "will result in frostbite and lead to hypothermia or death if precautions are not taken."
The forecast cold air is the product of a weather system called the polar vortex, a large cyclone that sits above the North Pole all year round. The bitter temperatures expected across the Northeast are being brought by a "piece" of this vortex that has broken off and traveled further south, Palmer said.
Before hitting the Northeast, temperatures will drop across the Midwest on Friday — with forecast lows of minus 7 in Green Bay, Wisconsin, and 2 below zero in Chicago. The icy blast will move through the Great Lakes on Friday night and into the Northeast on Saturday.
The bitter cold also is a precursor to a snowstorm forecast to move through the Midwest on Sunday and into the Northeast on Monday — although meteorologists say it is too early to predict the storm's exact path or power.
Between 6 and 10 inches of snow was possible in some areas of the Great Lakes on Friday, and light snow could fall in parts of eastern North Carolina, the National Weather Service said.
While the East was likely to be locked in a freezer the whole weekend, the West will feel like a different season with temperatures in 80s and 90s in California, Arizona and elsewhere, according to forecasters.
This article first appeared on NBCNews.com.