On 25th July 2019, geographers at the RWTH recorded the highest temperature ever measured in Aachen.

On 25th July 2019, the highest air temperature since the beginning of meteorological measurement in Aachen in 1901 was recorded: 40.0° C! This was the very first time that the mercury had reached 40.0° C. The previous records – established in 1911 (37.0° C) and 2015 (37.7° C) – had just been broken on the day before, 24th July 2019, with an air temperature of 38.1° C.

Clear proof of climate change, say scientists
The measurements were taken two metres above ground level at the weather station of the RWTH’s Department of Geography in Aachen-Hörn, which has been recording meteorological since 1980. The measurements were compared and confirmed with data from Station Aachen (weather station), which was operated by the German Weather Service (DWD) on Aachen’s Wingertsberg from 1901 to 2011. All; in all, this was already the eighth so-called “hot day” – a day with a maximum temperature of more than 30° C – in this year. Normally, we expect three to four hot days a year. In addition, it was the third day with a temperature in excess of 35° C. In what we are currently calling the “Normal Period”, from 1961 to 1990, the total number of days with a maximum temperature of 35° C in the whole period of 30 years was just four. Since 1991 there have been 29 such days.

Current weather conditions have been transporting masses of subtropical air from the Mediterranean region unusually far into Central Europe, according to RWTH scientists. Very high summer temperatures have often occurred in connection with comparable weather conditions, with increasing frequency since the 1990s, which is seen as clear proof of climate change. In cities, hot weather conditions are exacerbated by urban “heat island” effect due to sealed surfaces and buildings – an effect which has also significantly increased in recent years.