What started as a mild winter has turned into a freezing affair. According to DMI, Danish Meteorological Institute, Copenhagen experienced the largest amount of snow in one day in at least 13 years on Friday. Additionally, January 2026 has been the coldest January in 16 years.
Looking at the forecasts, it seems that warmer days are far off.
Monthly forecasts indicate that the cold will likely persist well into March.
Although climate researchers and meteorologists agree that we need to endure the winter cold a bit longer, there is disagreement about what is causing the harsh weather conditions. While a climate researcher from DMI points to a collapse of the atmospheric phenomenon known as the polar vortex, a Norwegian climate researcher offers a different explanation.
Acts like a leaky freezer
Martin Stendel, a climate researcher at DMI, says that a collapse or split of the polar vortex is the reason for the freezing temperatures across the country.
The polar vortex is a low-pressure area that sits as a large cold whirlpool and rotates counterclockwise over the North Pole, high up in the stratosphere.
Waves in the atmosphere transport energy upward, and approximately every other year, the waves high up in the stratosphere become too strong, increasing temperatures at the North Pole and weakening the polar vortex.
Such a polar vortex split acts like a leaky freezer: The wind belt that keeps the very cold air confined in the Arctic collapses and sends polar air down to our latitudes. After three to four weeks, it reaches the surface and hits with extreme cold in places like North America and Northern Europe.
However, Martin Stendel points out that this time there is a rarer event at play. The polar vortex wind is weaker than usual, which he attributes to increased circulation in the lower atmosphere. Normally, it is rarer for the cold air to hit Denmark.
»We saw it during the winter periods of 1978-1979, 1995-1996, and again in 2009-2010, when large parts of Northern Europe experienced very cold and harsh winter conditions, so it will likely be something similar we will experience this time«, says Martin Stendel.
In the winter of 1978, the most severe snowstorm in a hundred years hit. It particularly affected Lolland and Falster. The snowstorm lasted four days and stretched from December 28 into January.
The winter of 2009-2010 was the coldest in Denmark in 14 years, with an average temperature of minus 1.5 degrees.
In 2019, Politiken wrote about a weakened polar vortex, which at that time had significant consequences in North America, where temperatures in places like Chicago dropped to minus 30 degrees.
In practice, it takes about two to three weeks before we feel the effects of a weakened polar vortex at the surface. This suggests that the cold winter weather is not going away anytime soon.
Martin Stendel emphasizes that there is some uncertainty associated with the forecasts, making it difficult to predict precisely where and how hard the phenomenon will hit. But there is a fairly high probability that it will affect both temperature and weather conditions in Denmark.
»It is hard to say exactly how long it will affect us, but do not expect warmer temperatures in the next few weeks«, says Martin Stendel.
Andreas Nyholm is a meteorologist and physicist working at TV 2 Weather. Generally, the weather in Denmark and Europe is too chaotic to predict accurately far in advance, he emphasizes. But:
»There is an increased likelihood that the cold will continue beyond the next two weeks and further into March«.
For two reasons, he points out:
»One is that the polar vortex appears to be breaking down again, which can traditionally release the Arctic air. The other reason is that once we have the cold, there is a greater likelihood that it will stay«.
According to Andreas Nyholm, in 60 percent of the cases where the polar vortex breaks down, it results in polar cold.
Collapse or not?
Erik Kolstad, a climate researcher at the Norwegian institute Norce, sees a different explanation for the cold winter conditions. He explains that in November, we experienced a so-called stratospheric warming, which often brings cold weather in the following weeks and months. But according to him, it no longer plays a role in the current weather conditions.
When determining the conditions around the polar vortex, one typically looks at a forecast for the next six weeks. This involves examining the wind in the stratosphere.
»We look at wind direction and strength in the stratosphere at 60 degrees north. When there is a collapse, these winds completely collapse and even reverse direction. And that is not happening right now. But in a couple of weeks, it might look like they are weakening a bit«.
The result is essentially the same: The weather gets colder.
Normally, Denmark is affected by westerly winds coming in from the North Atlantic. Therefore, we typically have very mild winters with a lot of rain.
But according to the Norwegian climate researcher, the cause of the cold in Denmark is found to the east.
»Right now, the situation is reversed. Instead, we get winds from the east, where it is much colder. So there is a big difference. In Siberia and Russia, it is sometimes around minus 30 degrees, so it means a lot for the weather conditions where the winds come from«.
At DMI, they no longer make long-term forecasts. However, Martin Stendel refers to forecast maps from the European weather center ECMWF. Based on these forecasts, he maintains that there is a beginning collapse of the polar vortex.
He emphasizes that models can be wrong – especially when looking far into the future. However, he maintains that the situation and development over time have not changed much in recent forecast periods, which of course increases credibility.
