Washington, Jan 8 - A new Arctic blast threatened Thursday to blanket much of the US in deeper snow and sink temperatures into a deep chill as far south as Florida.

A weather expert at AccuWeather. com, Joe Bastardi, said the deep freeze threatened to turn this winter into the coldest and broadest cold siege since 1985. Temperatures have dipped to minus 40 degrees Celsius in the northern Midwest tier of Minnesota.

In more southerly states like West Virginia, daytime highs earlier this week never exceeded 17 C - a record low maximum.

Among the current storm fatalities were four adult special-needs students in Ohio being sent home from a vocational and rehabilitation school early because of snow accumulations near Dayton, the Dayton Daily News reported.

Their shuttle bus collided with a tanker truck that had lost control on an icy four-lane interstate highway, police officials told the News. Some of the occupants, adults with developmental and intellectual disabilities, were anchored to the bus in wheelchairs.

Florida orange and strawberry growers have been wrestling for days against freezing temperatures, and were bracing for worse with the newest Arctic air mass moving south that could even bring snow.

Ice wreaked havoc on the roads of Dallas, Texas.

"It'll be like the great winters of the '60s and '70s," said Bastardi.

The storm has already dumped up to 30 centimetres of snow on Chicago, Milwaukee, Indianapolis, Detroit and Columbus.

It was headed to Boston, New York, Philadelphia and Baltimore by early Friday morning.

Atlanta was bracing for five centimetres of snow. The South, where homes are built for warmer climate, could feel record breaking low temperatures.

Since early December, broad sections of the country have been chilled by snow and low temperatures, as several blizzards dumped high accumulations of snow upon the Plains, mid-Atlantic and New England.

"The cold air currently streaming across the Upper Midwest into the East and South will only compound the winter problems of the nation, especially since these depths have not been experienced across such a wide area simultaneously in decades," AccuWeather. com reported. (dpa)