What is frostrøyk? 

The first part of the word should give you a clue. Frost directly translates into frost. Røyk means smoke. Røyking means smoking, and just like in English, you can smoke something, like a cigarette, or use smoking to preserve food, as is the case with the Norwegian staple smoked salmon røkt laks. 

Smoking food has a long history in Norway. 

Frostrøyk, meaning frost smoke, occurs when cold air drifts over a warmer water surface. The air is supplied with water vapour, and saturation and condensation occur. 

The air that has been warmed up by the water causes the frost smoke to be swirled up in spiral moments. The condensation evaporates again when the frost smoke reaches a high enough altitude. 

The phenomenon is common in Norway during the winter, especially along fjords and the coast, when cold air from land drifts out to see. 

For the phenomenon to happen, there needs to be a 10c difference between the temperature and the water. This means that if you are seeing it during winter, it must be really cold. 

Frostrøyk is also referred to as sjørøyk, frosttåke, damptåke.