First is yesterday afternoon's sounding, with a 700-mb (10,000 ft) temperature of -18.5˚C, more than 3˚C colder than the previous record of -15.3˚C.
If you are wondering, temperatures aloft have already started to increase, so this morning's 700-mb temperature is -15.7˚C. That's not as cold, but it is the 2nd lowest on record.
Second is the overnight minimum temperature of 14˚F, which is the lowest temperature recorded in the month of October in Salt Lake City with records going back to 1874.
As of 3:37 AM the temperature at Salt Lake City fell to 14°F. This not only sets a record low temperature for today (10/30), but is also the coldest temperature ever observed in the month of October (records back to 1874). The previous record for both was 16°F (10/30/1971). #utwx— NWS Salt Lake City (@NWSSaltLakeCity) October 30, 2019
Beyond Salt Lake, it was cold everywhere, but as usual, Peter Sink, a sinkhole in the Bear River Range known for extremely low temperatures, takes the cake. Looks like a minimum temperature of -43.6˚F based on data available in MesoWest.
Logan meteorologist Timothy Wright tweeted this morning that the minimum was -45.5˚F and that would be a national October record. The lower temperature he reports could reflect that he has access to another station or data between the obs times reported to MesoWest. I'm sure he'll get to the "bottom" of this eventually.
National October record (lower 48) smashed again at Peter Sinks this morning. Been to -45.5F. (-43.1C) so far. Watch out Alaska, your record is in jeopardy too! 3 hours yet before sunrise. Headed to nearby Middle Sink to "chase" the cold air. #utwx #akwx @NWS @NWSSaltLakeCity pic.twitter.com/xM2yQA4xZf— Timothy E. Wright (@wrighthydromet) October 30, 2019
I would rate this event as one of the most remarkable since I moved here in 1995, up there with the 1999 Salt Lake City Tornado and Thanksgiving 2001 Hundred Inch Storm at Alta. Extreme cold surges are rare events in northern Utah. This is why, when one looks at the record daily minimum temperature records for Salt Lake City (light blue line below), there are a small number of truly exceptional minimum temperature records with a spike-like appearance. Examples include February 9-10, 1933, November 3, 1936, and November 15-16, 1955. There is another period in December during which cold surges in 1932 and 1972 set extreme minimum records from December 9-16.
Such cold surges are the meteorological equivalent of drawing a royal flush in five-card draw. A magic sequence of events must come together to get such extremely low temperatures. This is especially true given the warming global climate and urban heat island effects.
An alternative perspective on the extreme nature of the event is provided by the analysis below, which is a map of departures of current surface temperatures from the 1979-2000 average for each location (referred to as anomalies). The coldest anomalies are in western North America, centered over Wyoming. However, the global average is 0.7˚C warmer than the 1979–2000 average, so global warming is still a thing. Additionally, patterns that cause cold surgest into the western and central U.S. are often associated with anomalously warm temperatures in Alaska, and you can see that below. In fact, the high temperature in Anchorage yesterday was 54˚F.