The 2026 cold wave brought northern Fennoscandia its coldest 2‐week period since 1987

Abstract

During late December 2025 and January 2026, a severe and long‐lasting cold wave affected northern Fennoscandia. In this article, we aim to quantify the extremity of the 2026 cold wave and evaluate the atmospheric conditions that led to the persistent cold anomalies. Analysis of in situ temperature observations and ERA5 reanalysis indicates that the 14‐day period between 31 December and 13 January was the coldest 2‐week period since 1987 over a large area, and regionally since at least 1964. The cold wave was initiated by pronounced cold air advection and intensified through strong surface cooling beneath a persistent high‐pressure system.