Berlin is now one of the most heavily populated cities in the EU. As urban growth increases, the negative climatic effects that affect the health of the urban population and are exacerbated by the climate crisis also increase. In order to get a better measurement of the spatially highly differentiated urban climate variables (e.g., air temperature and heavy rain), the project implements weather observations according to the Citizen Science concept in an existing scientific measuring network, the Urban Climate Observatory Berlin (UCO Berlin). The monitoring stations used for this (MESSI) have been specially developed and tested at Freie Universität Berlin in cooperation with Technische Universität Berlin for use in Citizen Science projects. The 100 MESSI are set up and maintained by city residents, especially garden plot holders. The data obtained are jointly evaluated and published using a co-creation approach to specific scientific questions. The collected atmospheric data is then freely available via the open UCO Berlin.