When you are living outdoors and moving around in nature, you need to adapt your schedule to the weather. It is quite simply not a good idea to pitch your tent at the edge of a cliff in the archipelago if the forecast is predicting gale winds, just as you should not try to walk the trail’s most exposed mountain passes under the same conditions. Listening to the weather forecasts and planning your route based on these forecasts is an important part of planning for your trek, particularly when you are trekking in mountainous terrain.
It is in reality not entirely correct to talk about “mountain weather”, since the weather basically follows the same principles as in other areas of the country. But the openness of the landscape, the mountains and valleys, the large changes in altitude and other variations in the terrain determine the wind, temperature and precipitation. Different areas in the mountains can have completely different weather conditions - it can literally vary from one valley to the next. The largest difference, however, can be found between the high mountains and low-lying areas.
People usually say that the weather in the mountains can change quickly, but in reality the change is not as drastic as you may think. What is really happening is that we are moving between different types of weather, for example when we leave the mountain birch forest for the open plains of the high mountains.
Mountains press the wind upward...
Normally, the wind in the mountains runs southwest. Air is pressed upward by the mountain chain and cooled by higher layers of air. The resulting clouds then release precipitation in the form of rain or snow. This precipitation lands primarily on the side of the mountain from which the wind originates. This means that it is normal for there to be more precipitation in the westerly part of the mountains. In general, mountains have slightly more precipitation than the rest of the country but it is also here we find some of the parts of Sweden with the least precipitation – such as the area around Abisko. There the sun can be shining from a blue sky while it is raining cats and dogs not far away at Riksgränsen
...then the wind is squeezed together
In the high mountains, the wind can blow freely without any obstacles. A wind force at home that would be considered “windy” can turn into a “storm” in the high mountains. But it is not only the open plains that factor in here. When the wind is squeezed into valleys and mountain passes, the wind velocity can increase to a full storm even if the general wind force is not particularly high. The type of terrain in some places can also create fickle winds that do not behave as expected. For example, they can come from the “wrong” direction or suddenly sweep in with tremendous force.
Beware of the wind!
The wind has a gentler side that cools the air on a warm summer day. But in the mountains, combined with snow and cold temperatures, it can be dangerous. “Moderate to frisk winds” does not sound so bad, but at zero degrees, the wind chill effect on the skin falls to –13°C! If the wind speed increases, the wind chill is even colder. This is when things start to get dangerous - if you are tired and cold the risk that your body temperature will fall increases. This is called hypothermia and, while hypothermia may be mainly associated with winter treks, during the summer, for example at high altitudes, the cold, wind and rain can force a person’s body temperature to fall so sharply that the situation can become serious.
This is why it is important to be able to predict in advance if the wind is picking up and if the weather is taking a turn for the worse, so you can change your route, head home or seek cover
A wind sack is your key to safety in the mountains when it is difficult to find protection from cold winds.