The polar plunge over Minnesota and the Twin Cities is recoiling ever so slightly Tuesday, with temps around ice's melting point a possibility in a few more days.

In the meantime, hundreds of thousands of Minnesota kids are home from school for a second day Tuesday while morning commuters in the metro played bumper cars thanks to "black ice" forming on ramps and overpasses.

Just before midnight Monday, temperatures in the Twin Cities dropped to 23 below, the coldest in a decade and practically a generation.

The prolonged chill led to frustration for some AAA members who could not get through. Call lines were jammed Tuesday, the day after AAA Minnesota-Iowa set a record with 3,000 calls for help, said spokeswoman Gail Weinholzer. AAA Minneapolis, which serves only Hennepin County and a handful of adjacent suburbs, was also experiencing problems as call volumes were at capacity Tuesday, said spokesman Matt Hehl.

Both Weinholzer and Hehl suggest that motorists arrange for service through the AAA website or by downloading the free AAA mobile app. The app is compatible with iPhone, iPod Touch, iPad and Android Phones and available at AAA.com.

"It's far more efficient to use the website or app," Weinholzer said. She promised that those messages are being seen motorists won't have to wonder if their request has been seen.

By 1 p.m. Tuesday, thermometers had inched their way up yo zero degrees in the metro — a hopeful sign that weather forecasts are correct and the worst of the deep freeze plunge will soon be behind us. If Twin Citians look far enough west, they'll see readings in positive territory: 5 in Montevideo and Madison, and 3 in Marshall to the southwest.

But in the short run, motorists were facing another hazard Tuesday morning: icy roads. Black ice — that invisible layer that forms thanks to vehicle exhaust emissions — was making for slippery ramps, bridges and intersections.

A seven-vehicle pileup on northbound Hwy. 169 at 7th Street in Hopkins illustrated how dangerous conditions were as temperatures hovered around minus 12. The highway was closed for about 45 minutes.

On the other side of town, commuters in St. Paul on southbound I-35E got caught in traffic when a vehicle spun out and slammed into the concrete median near Maryland Avenue. The left lane was blocked for 30 minutes. Things didn't improve south of downtown St. Paul as a three-vehicle crash took out two lanes of southbound 35E at Hwy. 13.

In Little Canada, a pickup truck slid off of the icy I-35E flyover ramp, down to westbound I-694 and landed on a frozen-over holding pond. Fortunately, Anne M. Spiess' vehicle did not break through the ice. Spiess, 54, of Maplewood, was in fair condition Tuesday afternoon at Regions Hospital.

Police and the State Patrol responded to at least six rollovers between 5 and 9 a.m. The first happened just after 5 a.m. on Hwy. 212 at Hwy. 41 in Chaska.

"With the weather so frigid, heed our advice. Slow down! Don't hit black ice," the Minnesota Department of Transportation tweeted.

The National Weather Service (NWS) said Tuesday's high is expected to be near zero, and maybe above by a degree or two, then dipping down well below zero overnight, with temperatures in the teens-below in Minneapolis and colder than that in the suburbs. On Wednesday, the daytime high should be in the lower single digits above 0, then back to minus 10 overnight. The lower 30s are being dangled before Twin Citians iced-over gazes come Saturday and Sunday.

More schools remaining closed

After a state-mandated closing of public schools Monday, most districts decided to remain idled Tuesday during what the NWS has declared a "historic and life-threatening cold outbreak."

Frostbite patients swamped hospital emergency rooms in the metro area, far beyond what is typical by this point on the calendar.

Flights at Minneapolis-St. Paul International Airport were affected yet again Tuesday, with about 40 cancellations as of late morning, "most of which are likely weather-related," said airport spokesman Patrick Hogan.

"Like [Monday], the cancellations are spread across a wide geography: the Upper Plains states, the Midwest and the Northeastern United States are all affected," Hogan added.

Jefferson Lines bus serving the Twin Cities, elsewhere in Minnesota, the Dakotas and Montana was disrupted for yet another day Tuesday.

"The extreme conditions are causing mechanical issues with our buses," said Kevin Pursey, director of marketing and culture for Jefferson Lines. "We simply won't risk having riders or our employees stranded mid-route."

Among the major communities served by Jefferson feeling the impact: Minneapolis-St. Paul, Duluth, Fargo, Grand Forks, Sioux Falls and Billings, Mont. Specific route disruptions can be found at www.jeffersonlines.com.

Greyhound's latest service alert noted weather-related disruptions in Missouri, Indiana, Ohio, Illinois, Michigan, western New York state and points east.

The Minnesota Zoo reopens to the public Tuesday, after closing Monday due to the cold. Outdoor exhibits, including the Northern Trail and Minnesota Trail, will remain closed "in order to protect guests and animals," the zoo said in a statement.

And for those who have thawed out by the weekend and are not on a flight to the Caribbean, there's a chance to embrace Minnesota's signature season on Sunday afternoon at Edina's Winter Festival at Centennial Lakes Park, with horse-drawn sleigh rides, ice carvings, skating and sledding.

Star Tribune staff writer Susan Hogan contributed to this report. Paul Walsh • 612-673-4482 Tim Harlow • 612-673-7768