Weather experts at the Alaska Climate Research Center (ACRC) in Fairbanks say an “omega block,” basically a traffic jam in the atmosphere caused the unusual cold spell in December.
Temperatures in Interior, Southcentral and Southeast Alaska remained continuously below normal for over three weeks and dropped to “impressively low values,” according to the summary provided by the center at the University of Alaska Fairbanks.
“What makes this cold spell stand out is not just how cold it has been, but how long it has persisted,” said ACRC Director Martin Stuefer, who is also the Alaska state climatologist. “An omega blocking pattern locked the atmosphere into place for weeks, allowing Arctic air to repeatedly flood Alaska and produce temperature anomalies rarely seen for such an extended period.”
A strong area of high pressure settled over the Bering Sea in early December, while a deep low-pressure system formed over Siberia. Together, they steered frigid Arctic air southward into mainland Alaska and Canada’s Yukon Territory.
Other December highlights:
- Some regions had an exceptionally snowy month. Record snowfall occurred in Southeast Alaska. Several rounds of storms brought 50 inches of snow in Juneau, far above the December normal. Fairbanks also had more than double its normal December snowfall with a total of 23.7 inches.
- Sea ice extent across the Arctic continued its seasonal growth in December but remained at low levels. Sea ice extent was the fourth lowest in the satellite-era time series, ahead of 2016, 2017 and 2024.
- December 2025 precipitation measurements in Utqiaġvik indicate the wettest December on record, with a total water-equivalent of 1.4 inches, approximately six times the long-term monthly average. The measurements had not yet been confirmed, according to the summary, but would “represent a remarkable record.”
