Cold temps

Commuter Carrie Bauske, of Arlington Heights, waits for her train to arrive at the Arlington Heights Metra station as a cold snap took hold in the suburbs of Chicago on Thursday.

Records fell along with the temperature across the eastern United States on Thursday, as the coldest air of the season surged south. Friday morning's cold promises to be even more icy, taking aim at the Eastern Seaboard from Boston to Miami.

Temperatures in the Upper Midwest plummeted to as much as minus-35 Thursday morning. Widespread sub-zero temperatures were recorded from North Dakota to Kentucky and east into Pennsylvania and New York.

Frigid Thursday morning lows broke records in the Midwest and Ohio Valley. Chicago set a record low for the date of minus-8 degrees, breaking the old mark of minus-7 set in 1936. Cincinnati, Nashville and Springfield, Missouri, also broke record lows for the date, among dozens of other cities.

The Kentucky Mesonet observations stations recorded temperatures down to about 20 degrees below zero in the eastern half of the state, 30 to 40 degrees below average for this time of year. "For Bowling Green, Ky., and Paducah, Ky., Thursday morning was the coldest since Jan. 19, 1994, with lows of minus 7 degrees and minus 10 degrees, respectively," the Weather Channel reported. "In Lexington, Ky., the low of minus 7 degrees was the coldest temperature there since Jan. 27, 2003."

While Thursday might seem plenty cold enough for mid-February, Friday will be even more frigid as the plume of Arctic air digs in across the eastern United States. All-time February record lows are possible from Ohio to Virginia on Friday morning as temperatures plummet to as much as 40 degrees below average for this time of year.

Record low temperatures for the date are likely on Friday across many major Eastern Seaboard cities, including Boston, New York, Washington and Miami.

When combined with winds, the cold outbreak will lead to dangerous wind chills. Wind chill warnings and advisories stretched from the Upper Midwest to the Deep South on Thursday — even as far as Miami, where Friday morning lows around 40 degrees could break records for the date and surely will be the coldest air that southern Florida has seen in five years.

A freeze warning also was put into effect for the better part of the Florida peninsula for Friday morning. The National Weather Service warned that imminent, sub-freezing temperatures "will kill crops and other sensitive vegetation."

The week's record-breaking cold is courtesy of a plume of not just Arctic but Siberian air that has been trudging across the North Pole and into North America.

NOAA's Weather Prediction Center cautioned of continued, dangerous cold on Friday. "There are indications that this could be some of the coldest weather since the mid-1990s for parts of the Southeast U.S., Mid-Atlantic and central Appalachians," it wrote in a morning forecast update. "An eddy of the polar vortex will add to the potency of the surface cold front, thus creating a deep layer of bitterly cold air."

This warning was in far contrast with the above-average temperatures in the West, where record highs were recorded. On the north slope of Alaska, temperatures reached an astonishing 40 degrees above average on Thursday.

A strong ridge of high pressure has been building over the West this week, all the way north into the Arctic circle, which has not only brought extreme warmth over western North America but also has forced the eastern U.S. into its record-setting February cold snap.

As much of the eastern U.S. freezes in a bitter February cold snap, so too do the Great Lakes, which are now more than 85 percent covered in ice. With outlooks pointing to continued cold through the month, the potential grows for the Great Lakes to see one of the iciest years on record.

With a total ice cover of 85.4 percent, the lakes have now surpassed where they were at this time last year. After a brutally cold winter across the eastern U.S. in 2014, the Great Lakes went on to set the second-highest ice cover on record -- 91 percent -- since monitoring began in the 1970s. Ice lingered in Lake Superior through Memorial Day last year -- and it was even more surprising that it was still there as record highs were being broken in the Midwest. The record-highest ice extent occurred Feb. 19, 1979, when 94.7 percent of the network was covered in ice.

With 82.6 percent coverage, Lake Ontario seems primed to meet or exceed its record ice extent: 85.7 percent, set in 1979. Lake Erie is a popsicle with more than 98 percent of the lake covered in ice. As the shallowest lake in the network, it has reached full ice coverage three times on record, in 1978, 1979 and 1996. Erie's ice cover jumped in January, climbing from ice-free to 88 percent coverage in just a couple of weeks.