The culprit is an "arctic outbreak" that originated just above the US-Canada border, which is freezing temperatures across much of the US territory.
"Bursts" of cold air like this are usually confined to the Arctic region thanks to a series of low-pressure systems, says the NWS. However, one of these waves advanced through Canada and "escaped" to the US.
According to experts heard by Reuters, it is a vast mass of icy air in the atmosphere, which brings with it frigid temperatures - which can be prolonged if storms form.
From this information we can conclude that according to the US Weather Service (NWS), the culprit is an "arctic outbreak" that originated just above the US-Canada border, which is freezing temperatures across much of the US territory.
Learn more about arctic in brainly.com/question/1248314
