The exceptional heatwave at the end of June 2026 led to new records at the Ruhr University Bochum's climate monitoring stations. Both the Ludger Mintrop Urban City Station (LMSS) and the Rudolf Geiger Station (RGS) recorded the highest daily minimum temperature since the beginning of their respective measurement periods. Daily minimum temperatures reached 24.7 °C at the LMSS and 22.3 °C at the RGS, clearly exceeding all previous records.

While heatwaves are often characterized by their daytime maximum temperatures, daily minimum temperatures provide important information about the intensity of a heat event. They indicate how far the air temperature is able to decrease within a 24-hour period. Exceptionally high daily minimum temperatures therefore point to only limited cooling during the night and early morning hours.

The influence of the urban environment becomes particularly evident when comparing the two monitoring stations. The LMSS, located within the urban area of Bochum, recorded a daily minimum temperature 2.4 °C higher than the RGS, which is situated in a rural reference environment. This difference demonstrates that air temperatures in densely built-up areas cool down much less effectively than in the surrounding rural landscape, a characteristic feature of the urban heat island effect.

Such record values can only be properly assessed using long-term measurement series. Comparing the current observations with previous years reveals how exceptional the late June 2026 heatwave was. At the same time, continuous monitoring provides valuable insights into the long-term development of the urban climate and highlights differences in the impact of extreme heat events between urban and rural environments.