 DISCUSSION: Late January and early February of this year brought an outbreak of frigid arctic air to a large portion of the U.S. with temperatures in the north-central portion of the U.S. the coldest that they have been in over 20 years. Specifically, the coldest temperature measured this year occurred at Cotton, Minnesota of -56F on 27 and again on the 31 January. Including these temperatures this year, temperatures between -55 and -59F have been officially recorded 34 times in our ~150-year observation record over the continental U. S. (there are additional unofficial and/or unverified temperatures that have been measured below -55F). Given that we are past the climatologically coldest part of the year, this current outbreak of unseasonably cold air across the U. S. probably won't set any new record cold temperatures for the year.
For someone who lives in Louisiana, -56F is unimaginably cold. But, even colder temperatures have been recorded in the lower 48 states of the U. S. The map above shows the locations of the 15 official temperatures that have been measured at or below -60F. For the dates when these all occurred, please click here. Of particular note is the coldest temperature ever recorded in the continental U. S. of -69.7F on 20 January 1954 at Rogers Pass, Montana. This was so cold that the indicator of minimum temperature along with the fluid in the thermometer actually retreated into the bulb of the thermometer. The station that recorded this value existed in that location for only a short time from 1 May 1953 to 28 June 1956. It was installed next to a new mine which turned out to not be very productive. So, the mine and observation station were shuttered after only a short time. In order to achieve such an extreme temperature, conditions have to be just right. Otherwise, such a temperature would occur more often. Indeed, the weather conditions at Rogers Pass the night/morning of 20 January 1954 were ideal for generating extreme cold. In particular, there was fresh snow on the ground, a dry, cold air mass in place, no clouds, and no wind, all conditions very conducive to radiational cooling. In addition, the station was located in a depression allowing the coldest air to sink toward the station. Despite these conditions, and as is typically the case for record observations, this particular observation underwent a robust verification process by the Weather Bureau (precursor to today's National Weather Service). For example, the instrument was tested to make sure it was working correctly and the measurement was checked for consistency with other nearby stations. The above is a small glimpse into the coldest temperatures recorded in the continental U. S. and a little bit of the story surrounding the record coldest temperature. I suppose one take away from this is that no matter how cold it gets wherever you are in the lower 48 states of the U. S., it could always be worse (i.e., colder). To learn more about other past historic weather and science events from around the world, be sure to click here! ©2019 Meteorologist Dr. Ken Leppert II
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 Discussion: As the Midwestern United States begins to warm up, 30 years ago much of Alaska was following suit in what was a brutal end to the month of January. During the latter half of January 1989, temperatures across the interior portions of the state were reported as low as the negative mid-70s degrees Fahrenheit, which is shy of the record low of negative 80 degrees Fahrenheit in the state, but nonetheless an impressive and dangerous feat. Wind chills were even worse as an example below will illustrate. During this cold air outbreak, the highest pressure ever documented in North America (at the time) was recorded on January 31, 1989 in eastern Alaska at Northway. The pressure read 1078 mb (a reanalysis image shows the high pressure in red situated over Alaska). To put this in perspective, Siberia, where the highest pressures on Earth are typically recorded has maxed out in the mid 1080 mb range.  The above image was taken from Iowa State’s ASOS archive site. This is an observation from Cantwell, Alaska on January 28th, 1989. Notice the strong north/northeasterly winds with the temperature -43 degrees Fahrenheit making for treacherous wind chills.  What was the setup for this cold outbreak? High pressure leaked into Alaska from Siberia and the Beaufort Sea, locking cold air in place for about two weeks. This, along with a strong surface low pressure system (cool colors) to the south and a bit east of Alaska during the 28th created a difference in pressure which lead to a strong and persistent northerly to northeasterly wind (surface pattern and setup featured above). The observation above from PATW outlines what this particular day (the 28th) was like in central Alaska. To put this in perspective, a temperature of -43 degrees Fahrenheit and winds gusting up to 40 knots correlates to a treacherous wind chill of around -91 degrees Fahrenheit based on the National Weather Service Wind Chill Temperature calculator.  The last image shows the averaged 500 mb height anomalies across the region from the two-week period between January 17th to January 31st of 1989. A huge negative anomaly, signifying the polar vortex, has parked itself right over Alaska and areas to the north keeping the brutal and long-lasting cold air across much of the state. This was an impressive cold stretch, even for Alaska’s standards.
Be sure to stay tuned to GWCC for more interesting historical weather here! ©2018 Meteorologist Joe DeLizio Sources: https://www.adn.com/features/article/recalling-frigid-1989-alaska-winter/2011/11/21/  On January 31, 1958, the United States successfully launched the Explorer I satellite. As the country’s first successful satellite, Explorer I effectively marked the beginning of the U.S. Space Age. Additionally, the launch of Explorer I came as a direct response to the Soviet Union’s launching of Sputnik 1 & 2, launching the U.S into what was known as the Space Race. Following the success of Explorer I, the U.S. began developing and launching additional satellites, eventually paving the way for the satellites used in meteorology today.
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