Temperatures crashed to zero as far south as Kansas today as a huge mass of arctic air moves southward, leading some cities to open shelters.

School delays were common across Nebraska as districts worried about children standing in the cold at bus stops. Morning lows across western Nebraska were all below minus-15 degrees Monday.

The sharp cold wave came on the heels of a blizzard that halted travel in parts of the northern Plains during the weekend.

Schools closed today in parts of Minnesota and both Dakotas because of slippery roads and the cold.

Major highways in northern and western Minnesota had reopened after Sunday's snowfall of up to 14 inches, but schools in more than 100 cities closed or opened late today. In addition to snow-covered roads, the wind chill at 6 a.m. in Morris, Minn., was 41 below zero.

Interstates 94 and 29 reopened throughout North Dakota, where more than a foot of snow fell in places, but the entire state was under a wind chill warning as Monday morning lows included 25 below zero in Dickinson and Williston. Meteorologists said the wind would make it feel like more than 40 below.

"You need two parkas," National Weather Service meteorologist Patrick Ayd said Sunday in Bismarck.