School was called off Monday for the entire state of Minnesota, as well as cities and districts in Wisconsin, Illinois, Indiana and Iowa, among others.
Chicago Public School officials also cancelled classes for Monday ahead of the expected bitterly cold temperatures.
Southern states were bracing for possible record cold temperatures, too, with single-digit F highs (highs from minus 13 to minus 17 C) expected Tuesday in Georgia and Alabama.
Temperatures are expected to dip into the 30s F (single digits C) in parts of Florida on Tuesday.
But Florida Citrus Mutual spokesman Andrew Meadows said it must be at 28 degrees F (minus 2 C) or lower four hours straight for fruit to freeze badly.
