cold wave

A notable cold episode due to the invasion of an air mass of polar or arctic origin, at a very low temperature (well below 0°C), covering an extensive stretch of territory and lasting at least three days. Some cold waves last several weeks, during which the intensity of the cold fluctuates, with several peaks reached at which the lowest temperatures are attained. As happens with heatwaves, there is no unified definition of a cold wave, with each NMS establishing its own criteria and thresholds. Usually, the minimum temperatures reached during the coldest months of the year are taken as a reference, based on the normal (climatological) behavior of temperature in the territory in question.