Climatological Cold Waves in Norway - a base for Operational Warning System

Temperatures are increasing, and cold days and prolonged cold periods are becoming less frequent, even in high latitude regions such as Norway. Even though certain years a cold regime occurs and the temperature is low for a period. The Norwegian Meteorological Institute (MET Norway) is currently exploring methods to monitor cold waves, and possibly implement an operational warning system for cold waves or low temperature events in the future. 

Cold periods for Norway were analysed for the climatological periods 1961-1990 and 1991-2020. For spatial analyses, an observation-based dataset on a 1 km grid was used. In addition, observations from selected weather stations were studied to capture local effects. Cold periods were identified using different temperature limits of minimum temperature. 

A questionnaire was distributed to municipalities across Norway to assess the consequences of cold waves. The survey investigated which measures are implemented during cold periods and the temperature thresholds that trigger action. The responses indicate that cold weather alone is rarely a major issue. However, in combination with other events it becomes a significant contributing factor. The most frequently reported challenges were related to water supply and sewage systems, as well as power outages and heating. Measures and temperature thresholds vary considerably, including support for vulnerable groups and the provision of emergency water supplies. Some municipalities restrict children’s outdoor activities at −10 °C, while others maintain normal operations even during severe cold. Both the duration of cold periods and rapid temperature fluctuations are highlighted as key challenges.

Internationally, a range of thresholds are used to define cold waves and trigger low temperature warnings. MET Norway aims to develop a method suitable for Norwegian conditions, potentially in collaboration with neighbouring countries. Climate Services has worked in cooperation with the forecasting division at MET Norway to propose a unified methodology applicable to both forecasting and climatological analyses, ensuring consistency across services. After finding a suitable definition for cold waves or warning of low temperatures, it will be tested operationally and evaluated.