A vortex of super-chilled northern air leads to school closures

The recent cold in Minnesota and across the nation, according to weather forecasters, was the result of a “polar vortex.”

At about noon on Monday, Hermann Insurance Services’ outdoor digital thermometer read a chilly -17 degrees. Photo by Derrick Knutson

At about noon on Monday, Hermann Insurance Services’ outdoor digital thermometer read a chilly -17 degrees. Photo by Derrick Knutson

The polar vortex is circulation of strong, upper-level winds that normally surround the northern pole in a counterclockwise direction — a polar low-pressure system, according to online information from meteorologist Brandon Miller. These winds tend to keep the bitter cold air locked in the Arctic regions of the Northern Hemisphere. It is not a single storm. On occasion, this vortex can become distorted and dip much farther south than it would normally be, allowing cold air to spill southward.

Sustained cold at this level in Minnesota has not been experienced in Minnesota for more than a decade.

Both North Branch Area Public Schools and Rush City Schools were closed Monday and Tuesday as a result of the frigid temperatures. Gov. Mark Dayton closed schools Monday.

A Minnesota governor has not ordered schools closed across the state since Arne Carlson did it Jan. 16, 1997.

Some outlying areas of Chisago County reportedly were 25 or more degrees below zero Monday, but that’s still well off the state record.

On Feb. 2, 1996, a low of -60 degrees was recorded near Tower, according to information from the Minnesota Department of Natural Resources.

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