Ongoing Cold Snap in NW North America
Long duration deep cold is here.
Northwest North America, but especially the Yukon Territory and eastern Alaska, are in the midst of what is shaping up to be a historically long cold snap. I posted a brief summary earlier in this month regarding the initial phase of the event, here. I’ll have a more in-depth summary in early January as this is certain to be the coldest December in decades in the region.
Following a very mild autumn and first few days of December, an abrupt change in the large scale pattern occurred December 3-5, and since then deep cold has been entrenched. So far at least, the duration is more notable than the absolute lowest temperatures. In Alaska, except in Southeast Alaska, there have been no new daily record low temperatures set at any of the long term climate sites (Northway tied the existing record low on December 22). Since the very cold pattern is going to persist past New Years, especially in Alaska north of the Alaska Range and in the central and northern Yukon, it seems like a post to provide some backstory would be useful.
2025 cold snap so far
The duration of the cold is partly reflected in just how far below normal the average temperature for the month is through the first 26 days of the month. The core of the departures, in the Yukon Territory, are close to 20°C/36°F below the 1981-2010 baseline in the real-time monitoring courtesy Karsten Haustein (Fig 1).
Site specific lowest temperatures reported through December 26 show a fairly marked west to east gradient, with the lowest temperatures in easternmost Interior Alaska and in the Yukon Territory (Fig. 2). The lowest temperatures from Fairbanks north and westward to this point are not especially notable for this time of year. The lowest temperature I have found confirmation of is -52C/-62F at Faro, YT and Chicken, Alaska.
Cold snap duration
The duration of cold snaps (anywhere) are somewhat subjective. Are cold snaps defined by the temperature (high, low, average?) being lower than some threshold, or is it based on the the magnitude of departures from normal? Does a one or two day break in the cold “reset the clock”, and what’s the definition of a break? And of course, when looking across a region, the details will vary somewhat place to place.
Historic long duration winter cold snaps
An old-school forecasting rule of thumb is the large scale flow patterns that support Alaska and Yukon cold snaps don’t last more than about four weeks before breaking down. Like most rules of thumb, that works pretty well, but there have been several longer events over the decades. If some of your “favorite” cold snaps aren’t listed below, it’s probably because they did not last longer than about 30 days, e.g. Jan-Feb 1947, Dec 1961, Jan 1971, Dec 1980, Jan 1989, Jan-Feb 1999, Dec 2008-Jan 2009, Jan 2012.
Winter 1908-09: this extended cold snap was especially-long lasting in the Alaska-Yukon border county. At Dawson, YT, the temperature remained at or below -20C (-4F) from Christmas Day 1908 until February 17. At Eagle, there were a couple of breaks with all but 8 days (not consecutive) between December 28 and February 17 had high temperatures of -10F or lower.
Winter 1917-18: temperatures widely stayed well below 0F across a large portion of mainland Alaska and Yukon from late November until early January. The Fairbanks Ag Experiment Farm high temperature for December was -11F (-23.9C), the only calendar month on record with a high temperature below 0F (-17.8C). Other high temperatures during December 1917 included -31F at Fort Yukon and -35F at Dawson, YT.
Winter 1924-25: early January to mid-February. At Tanana, temperatures remained 0F or lower on 40 straight days, January 2 to February 10. At Dawson, YT, 15 consecutive days had high temperature of -40C/F or lower
Winter 1964-65: early December through mid-January. At Dawson, YT the low temperature was -40C/F or lower 32 of 33 days December 10 through January 11. At Northway, every day except two between December 8 and January 15 had a high temperature of -8F (-22.2C) or lower.
Winter 1968-69: Northway temperatures 0F or lower December 23 to February 10. At Dawson, temperatures -17.8C/0F or lower December 17 to February 10. Whitehorse had only one day above -17.8C/0F between December 27 and February 6.
Winter 2019-20: Although there were a couple of moderate breaks, mid-December 2019 to the first days of February 2020 were mostly much colder than normal in Interior Alaska and the Yukon.
Possible records in the 2025-26 cold snap
While I don’t want to speculate too much on how this cold snap will play out, here’s some of the streaks that I’m watching:
Fairbanks airport: daily low temperature -15F or lower every since December 4. Record is 38 days.
Tanana: daily low temperature -10F or lower every day since December 3. The record of 53 days is likely safe but could be a “top 5” longest.
Eagle (cooperative): daily high temperature below 0F every day since December 5. Record is 40 days.
Data Sources
NWS and ASOS and cooperative observation data available through xmACIS, here.
Natural Resources Conservation Service SNOTel data available here.
Yukon Territory climate data available here.
Real-time global climate temperature anomaly graphics are available from K. Haustein’s website here.
If this long duration cold snap materializes, will there be any consequences for the lower 48?