The North America snow cover lagged below normal during mid-autumn thanks to a warm Canadian climate while advection snows across the open water north of Eurasia during October allowed snow cover to build above normal during mid-autumn for the 15th straight year.

Generally, sudden stratospheric warming (SSW) events capable of producing arctic outbreaks are considered more likely during easterly phase of the quasi-biennial oscillation (-QBO). Past winter seasons when -QBO was developing in November, similar with 2025, and peaking during the winter season, similar with winter 2025-26 expectation, are identified (since 1979).