CHICAGO/CLEVELAND, Ohio, Jan 6 (Reuters) - A blast of Arctic air gripped the vast middle of the United States on Monday, with the coldest temperatures in two decades threatening lives, forcing businesses and schools to close and canceling thousands of flights.
Shelters for the homeless were overwhelmed and oil production could come to a standstill as the severe cold, described by some meteorologists as the "polar vortex" and dubbed by media as the "polar pig," brought temperatures below 0 degrees Fahrenheit (minus 18 Celsius).
Temperatures were 20 to 40 degrees F (11-22 C) below average in parts of Montana, North and South Dakota, Minnesota, Iowa, Wisconsin, Michigan and Nebraska, according to the National Weather Service.
The Arctic air was moving toward the east coast where temperatures were expected to fall throughout Monday to about 0 Fahrenheit on Tuesday. The coldest temperatures in years were expected in southern states.
"Cold temperatures and gusty winds associated with an arctic air mass will continue dangerously cold wind chills as far south as Brownsville, Texas and central Florida," the National Weather Service said.
The cold threatened to disrupt oil production, particularly in North Dakota, which could push fuel prices higher, analysts said. It also stalled shipments of grain and livestock and posed a threat to the dormant winter wheat crop.
In Cleveland, Ohio, where the temperature was 6 F (minus 14 C) and was forecast to drop to minus 7 F ( minus 22 C) overnight, homeless shelters were operating at full capacity. Shelter operators had begun to open overflow facilities to accommodate more than 2,000 people who had come seeking warmth.
"There are also going to be people that won't go into the shelters," said Brian Davis, an organizer with Northeast Ohio Coalition for the Homeless. Frostbite can set in within minutes at temperatures as low as Cleveland was experiencing, according to experts.
The National Weather Service issued warnings for life-threatening wind chills in western and central North Dakota, with temperatures as low as minus 60 F (minus 51 C).
The frigid temperatures in the United States mirrored or outdid those in such parts of the world as Almaty, Kazakhstan where it was minus 4 degrees F (minus 20 C); Mongolia, where temperatures reached minus 10 degrees F (minus 23 C) and Irkutsk, in Siberia, where it was minus 27 degrees F (minus 33 C).
Some 3,364 flights were canceled and 3,155 delayed, according to FlightAware.com, which tracks airline activity.
More than half of the flights into or out of Chicago's O'Hare International Airport were canceled. The afternoon temperature in Chicago was minus 14 Fahrenheit (minus 25 C). The last time Chicago was so cold was February 1996, according to Accuweather.com.
After five days of scrambling to catch up from storm delays, JetBlue said it would halt operations at three airports in the New York area and Boston Logan International Airport from 5 p.m. ET (2200 GMT) Monday until 10 a.m. ET (1500 GMT) on Tuesday to give crews time to rest.
The intense cold, which followed a storm last week that dumped up to two feet (60 cm) of snow on parts of New England, took a toll on traffic at U.S. retailers, as shoppers opted for the comforts of home over icy roads and frozen parking lots.
Retail consulting firm Customer Growth Partners estimated that nationwide, store traffic fell 4 percent to 5 percent from Jan. 2 through 5, the final four days of the holiday shopping season. The cold did spark demand for cold-weather gear, said Customer Growth Partners president Craig Johnson.
"Outerwear sales went through the roof," Johnson said. He said home improvement chains including Home Depot Inc and Lowe's Cos Inc were able to sell snow blowers and other snow removal equipment at full price, rather than at a discount at the end of the season.
The intense cold could affect oil production at companies such as Continental Resources, Marathon Oil and Hess Energy because conditions in North Dakota limited workers' ability to function.
"It is so cold that they cannot produce at full capacity, if at all," said Carsten Fritsch, senior oil analyst at Commerzbank in Frankfurt.
From Minnesota, no stranger to cold weather, to normally warm Atlanta, unusually frigid conditions prompted scattered school closures. In Chicago, officials who had initially planned to keep schools open on Monday closed them after protests from the teachers union.
"It's a far cry from the days when our parents used to say 'I used to walk uphill both ways in a snow storm to get to school,"' said Oklahoma City filmmaker Cacky Poarch, 45, the mother of two children. "Now, we just say, 'It's cold. No school today."'
Indiana was particularly hard hit. Offices and schools were closed in Indianapolis and businesses were asked to close at least until noon, if not all day.
Many people did not have the luxury of staying home.
In the western Chicago suburb of Geneva, Beth Anderson was shoveling the remains of Sunday's snow from her driveway before sunrise on Monday while warming up her pickup truck for the short drive to her job at a mall.
Anderson, 38, was well wrapped up against the bitter cold and was cheerful about the weather.
"I just wish I could get the day off too but it would take more than a bit of weather to close down the mall where I work," she said. Asked about the bitter temperatures, Anderson shook her head. "This is the Midwest, this is what winter is supposed to be like. It's been a while, so we were due for a cold one sooner or later."