Pakkasjaksot

Pakkasjaksot refers to extended periods of subfreezing outdoor temperatures, a concept widely used in Finnish meteorology. In practice, it denotes several successive days with temperatures at or below 0 °C, and may extend to weeks of continuous cold. The term emphasizes duration and persistence rather than a single day’s low temperature.

Causes are typically Arctic air masses or long-lasting high-pressure systems that clear skies and promote radiative cooling, especially in winter. Such episodes are more common in northern latitudes and occur when weather patterns block milder air from moving south.

Measurement and definitions vary by context. Meteorological agencies may define a pakkasjakso by the number of consecutive days with daily mean temperatures below freezing, or by minimum temperatures beneath a chosen threshold. Thresholds such as -5 °C to -15 °C or similar range are used depending on the purpose. Consequently, the perceived severity can differ between regions and years.

Impacts include increased energy demand for heating, potential frost damage to crops and infrastructure, and safety risks from icy conditions. Urban areas may experience more pronounced effects from cold snaps due to heat loss and vulnerable populations.

Overall, pakkasjaksot are a notable feature of Nordic winter climates and are monitored by national meteorological services, such as the Finnish Meteorological Institute, which issue warnings and seasonal outlooks based on upcoming cold spell potential.