(CNN) -- As it continued its northward retreat, the arctic blast still held sway over the upper Midwest, where it bore down with below-zero lows early Thursday.
This should be its last stand in the United States, as temperatures bump up day by day, the National Weather Service said.
Minnesota's coldest spots were forecast to plunge to as low as minus-30 degrees Fahrenheit with a frost-biting wind chill factor near 40 below.
Most of the nation should drop below freezing overnight, according to the NWS.
The polar vortex left behind ticking time bombs of sorts, and as it gives way to warmer weather, they are going off.
Pipes that froze and cracked are unfreezing, and plumbers and fire crews are rushing to stop the gushing water leaks, CNN affiliates are reporting.
The spurts caused some serious damage to homes and businesses and flooded streets.
Leaking pipes that broke during the freeze closed down a 30-story office building in Kansas City, Missouri, after its basement flooded, taking down central electrical circuits, KMBC reported.
More than 50 apartments were damaged when pipes broke in a building in Chattanooga, Tennessee.
Phones rang hot at plumbing companies from Memphis to Decatur, Alabama.
"Good for business. Bad for sleep," Decatur plumber Chris Byrd told WAAY. "It's about a once-every-10-year event we get something like this."
The changing weather is laying down thin ice patches from western Tennessee to eastern Kansas and Oklahoma, the weather service warns.
As warmer air moves in, it is bringing rain, drizzle and fog, which are bumping up against temperatures still below freezing.
The result is what the NWS calls a "wintry mix" -- everything from freezing fog to snow.
It will ice over streets, but slicken bridges and overpasses in particular and possibly tear down some power lines, the weather service said.
It's another nasty leftover from the polar vortex, which authorities have blamed for as many as 23 deaths across six states.