Over the past ten years, there have been an average of nine tropical nights at at least one measuring station in the country, according to the SMHI's temperature data. Tropical night means that the temperature does not drop below 20 degrees.
So far this year, there have been 19 tropical nights around Sweden. During the period 1961-1990 – which is used to study climate change – the average was 2.5 tropical nights per year.
The tropical nights are most common at the end of summer, when the sea and lakes are at their warmest. Many people experience that it is difficult to sleep during warm nights, but there are also clear health risks. New studies have investigated the consequences of high minimum temperatures, says Petter Ljungman, cardiologist and associate professor at the Karolinska Institute.
There, one can see that it increases the risk of death or the risk of stroke. This has been seen in Europe, in Barcelona, London and in Germany, but also in Asia, he says to Ekot.
