Lightning and thunder are often considered a summer phenomenon. But that’s not entirely true. However, lightning and thunder are much less common in the winter. In November 2021, a lightning warning was issued for the first time in winter. Thunderstorms are expected in northern parts of Nordland on Tuesday, and that is quite unusual. Climate watcher at the meteorologists, Reidun Skaland, can tell you. How do lightning and thunder occur? Summer often brings warmer weather and higher humidity. In order for lightning and thunder to form, we must have unstable weather conditions. In other words – a rapid temperature change, she explains. Photo: Mai-Linn Finstad In summer this is common, especially in south-east Norway, because the sun heats up the ground. Which causes the air closest to the ground to also become warm. – The warm air is lighter than the cold air and rises. When the moist air rises, it will cool and could form a storm cloud. In unstable air, the cloud can move quickly upwards and create a lot of wind. Raindrops, snow or hail will eventually form which will drag the air downwards and create a strong downward wind. This creates large electrical voltage differences inside the cloud – in other words: lightning and thunder. In winter, a slightly different process takes place. Greatest effect in winter In winter it is not solar heating of the ground that is the driving force. Then thunderstorms often occur along the coast because the sea is warmer than the air. – Preferably when cold air comes from Greenland, says the climate watchdog. Then storm clouds form over the sea, which drift towards the coast and create rainfall and lightning activity when the air masses rise over land. The lightning strikes in winter come from a lower part of the cloud. Therefore, there is more electricity left in the lightning when it hits the ground and the effect of the lightning strike is greater. Photo: NTB scanpix / NTB Tema More lightning strikes along the coast in winter – In winter, the most lightning strikes are along the coast from Western Norway and northwards, while in summer it is in South-East Norway and the Finnmarksvidda that the most occur, says Skaland. In winter there are generally few lightning strikes compared to summer. Therefore, overall, for the year there is most lightning in south-east Norway and on the Finnmarksvidda and least lightning activity along the coast in northern Norway and in parts of the mountains in southern Norway. The number of lightning strikes in Norway each year varies greatly. The statistics go back to 2014. In that year, over 660,000 lightning strikes were recorded, more than half of which took place in July. But in 2017, less than 39,000 lightning strikes were recorded, says Skaland. – But just under 300 lightning strikes per winter season are recorded. What do you have to think about when there is a thunderstorm? According to Skaland, there are several things you should think about if you are in a thunderstorm: Do not go under trees. Do not be in places where you will be the highest point, for example in an open plain. In that case, it’s a good idea to lie down. Do not go fishing or swimming.
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Lightning and thunder in winter
