A bitterly cold air mass spread across the western states and into the Plains and Midwest during the first week of December. One of the coldest temperatures recorded happened the morning of Saturday, Dec. 7, when the temperatureinJordan, Mont.dropped as low as -42!

In some cities, the frigid air mass has been the coldest seen in years or has broken daily record lows. Here's a few examples:

Billings, Mont.: Low of -21 degrees Saturday at the airport was the coldest reading at that location since Jan. 13, 1997, nearly 17 years ago.Miles City, Mont.: Not to be outdone, this southeast Montana city dropped to -36 degrees Saturday, its coldest since a -37 was recorded Jan. 30, 1996.Great Falls, Mont.: Low of -33 degrees on Saturday was the coldest temperature recorded so early in the season. Previous record was Dec. 8, 1972 (-36 degrees).Medford, Ore: Record low of 18 degrees on Wednesday and a record low of 14 on Thursday. According to the National Weather Service, this is the coldest air mass in the city since 1998.Pullman, Wash.: Sunday morning's preliminary low of -11 degrees was the city's sixth consecutive daily record low and the earliest it's gotten that cold in 74 years of recordkeeping.Denver: Record low of -13 degrees on Wednesday beat the old record of -5 degrees set in 2008. Thursday's low of -15 tied the daily record. Denver dropped to -13 degrees on Saturday morning, tying another record low.Ely, Nev.: Record low of -17 degrees on Wednesday crushed the old record of -5 degrees. Record lows were also set on Thursday (-23 degrees) and Friday morning (-19 degrees).Casper, Wyo.: Record low of -22 degrees on Wednesday beat the old record of -11 degrees set in 1972.Portland, Ore. and Astoria, Ore.:Three straight days with daily record lows Tuesday through Thursday.Spokane, Wash.: Saw its first high in the teens since Feb. 26, 2011 on Thursday.Glasgow, Mont.: Recorded its first subzero high temperature since Jan. 18, 2012 on Thursday.Daily records lows set on Saturday morning in Grand Forks, N.D. (-24 degrees) and Kansas City, Mo. (1 degree - tie).Sunday morning brought a record low of 7 degrees to Bishop, Calif. (old record 8 degrees)The coldest spot in the United States Sunday morning, was Havre, Mont., where the low temperature reached -37 degrees!

MORE ON WEATHER.COM: Arctic Photos from Destination Uncharted