Story highlights Three-quarters of the country will see freezing temperatures this week

The coldest polar plunge since last winter

(CNN) Record-breaking wintry temperatures are gripping the eastern two-thirds of the country, signaling that this could be one of the coldest seasons in years.

Across the United States, 76 locations have shattered their daily record cold high temperatures for December since the beginning of the month. That means some towns saw their coldest December day ever.

The bad news is that it's going to get even colder for the rest of the week. Below-freezing temperatures are expected for 7 percent of the country -- in fact, most of the country will see the coldest air since last winter.

This storm pattern is reminiscent of the 2014 Arctic outbreak that started a social media trend called the " polar vortex ."

The term took off, especially on Twitter, and meteorologists have been trying to clarify to the public what the name means. The polar vortex always exists near the north pole. An upper-level meteorology pattern called the polar jet stream locks in the cold air to the Arctic. Occasionally this northern jet stream meanders south and ushers in the polar air deep into the southern regions of North America.

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