Microclimate in the Cologne Bay Here’s why it’s often so humid in Bonn
Bonn · With an average of 35 muggy days, Bonn is far ahead of other German cities. But how much does the weather really influence our well-being? And why is it always so humid in Bonn of all places?
Does Bonn's climate make you „mööd“ (=tired)? With an average annual temperature of 12.1 degrees, the German capital is one of the warmest regions in Germany. A maritime climate is influenced by the Gulf Stream over the Atlantic and by the North Sea, which is only a few hundred kilometers away. With high relative humidity and rising temperatures, sultry days then increase in the federal city - to an average of 35 per year since 2019, according to Bonn University.
As Björn Goldhausen of the Bonn-based weather service WetterOnline explains, there were 16 very hot days around the weather measuring station at Cologne/Bonn Airport in 2020. These are days on which temperatures cracked the 30-degree mark. The number of summer days is significantly higher: "In the region, there were 61 summer days with 25 degrees or more last year," says Goldhausen.
At Cologne/Bonn Airport, there was only one night in 2020 when the temperature was below 20 degrees. Those are the so-called tropical nights. "But as soon as you look in the cities, the value increases significantly. In the cities, we usually measure eight to 10 tropical nights," he says. These are signs of mugginess or extreme heat, "so that's exactly what we're going to get in the coming days," Goldhausen says.
In Bonn, the average temperature in 2020 was as high as 13 degrees, according to evaluations by Klaus Kosack, former chief statistician for the city of Bonn. Since 1895, annual temperatures have increased by two degrees Celsius on average. On 26 days last year, the mercury column climbed above the 30-degree Celsius mark, and 75 summer days with more than 25 degrees Celsius in the shade were recorded.
Bonn is surrounded by low mountain ranges at the southeastern end of the Cologne Bay, which means there is little movement in the air masses. As a result, it is often oppressively warm in the city, not infrequently five degrees warmer than in the surrounding area. The location can also lead to inversions, which increase particulate pollution. Some people feel sluggish and dull as a result. Also because the human body has difficulty regulating the sultry heat.
As the German Weather Service (DWD) explains, the body sweats because of the heat - this is good regulation in dry conditions, and works even better in windy conditions. If it is humid, the air can no longer absorb the water from the pores of the skin. A "congestion" occurs and the perceived temperature could be quite a few degrees above the measured one.
According to the DWD, sultry weather conditions can affect the well-being, performance and health of people with cardiovascular and inflammatory rheumatic complaints. If the weather situation changes within a very short time, some people even complain of headaches and scar pain.
(Original text: Sebastian Meltz and Jill Mylonas; Translation: Mareike Graepel)
