By Ellen Wulfhorst
NEW YORK, Jan 6 (Reuters) - A blast of Arctic air gripped the mid-section of the United States on Monday, bringing the coldest temperatures in two decades, forcing businesses and schools to close and causing widespread airline delays and hazardous driving conditions.
Meteorologists said temperatures were dangerously cold and life-threatening in some places, with 0 degrees Fahrenheit (minus 18 Celsius) recorded in Chicago, St. Louis and Indianapolis. The chill was set to bear down on eastern and southern states as the day wore on.
The frigid temperatures in the United States mirrored or outdid those in such parts of the world as Almaty, Kazakhstan where it was minus 2 degrees F (minus 19 C); Mongolia, where temperatures reached minus 10 degrees F (minus 23 C) and Irkutsk, in Siberia, where it was minus 24 degrees F (minus 31 C).
In the United States, temperatures were 20 to 40 degrees below average in parts of Montana, North and South Dakota, Minnesota, Iowa, Wisconsin, Michigan and Nebraska, according to the National Weather Service.
It issued warnings for life-threatening wind chills in western and central North Dakota, with temperatures as low as minus 60 F (minus 51 C).
"Cold temperatures and gusty winds associated with an arctic airmass will continue dangerously cold wind chills as far south as Brownsville, Texas and central Florida," the National Weather Service said.
The last time Chicago was this cold was February 1996, according to Accuweather.com.
"The Arctic cold front responsible for the frigid blast will move through the East Coast Monday into Monday night and bring the coldest temperatures some have experienced in twenty years," said Accuweather.com weather writer Mark Leberfinger.
Oklahoma City and Tulsa schools were closed because of the extreme temperatures.
"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,'" Poarch said.
The Arctic airmass will slam the eastern two-thirds of the country through mid-week, the National Weather Service said.
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, due to temperatures and wind chill conditions.
Widespread wind chill warnings and advisories were issued from eastern Montana and Wyoming through Minneapolis, Chicago and St. Louis to the Atlantic seaboard.
The extreme cold can cause frostbite or hypothermia in people and in pets in as little as five or 10 minutes, according to meteorologist Fred Allen in a report for WeatherBug.
Excessive delays were reported at airports in Indianapolis, Minneapolis, Chicago, Cincinnati, Cleveland and St. Louis.
Farmers in the Plains states of Nebraska and Kansas were worried that the subzero temperatures would kill off part of the new winter wheat crop which, while typically hardy, cannot always tolerate extremely low temperatures.
Ranchers in South Dakota were keeping an eye on cattle herds, as hundreds of calves were being born in the life-threatening cold.
In Kansas City, where wind chills were forecast at -20 to -40 degrees F (minus 29 C to minus 40 C), schools were closed. Some roadways were shut down after slick conditions triggered multiple early-morning collisions.
Lake-effect snow was set to barrel in off the Great Lakes, dumping two to three feet of snow to the east and southeast through Wednesday, meteorologists said.