The heatwave in summer 2003, with around 70,000 casualties, was one of the most devastating natural disasters in the last 100 years in Europe. It showed what an impact such extreme weather conditions can have. It also showed, however, that the most severely affected areas are European cities. On the one hand, heat leads to significantly higher mortality rates, on the other hand it also compromises the quality of life, including the quality of public spaces. In 2014 a share of 54% of the worlds population lived in cities. For Europe this share will rise to 73% until 2050 (see United Nations 2015,1). In view of ongoing urbanisation, this entails significant problems for European cities. Owing to their dense development, cities have urban heat islands that will intensify considerably in forthcoming decades due to climate change. Apart from increasing average temperatures every year, cities can expect prolonged periods of heat in terms of intensity and frequency, characterised by high maximum daytime temperature and at the same time reduced nocturnal cooling. The city of Vienna, for example, the focus of this work, will have to be prepared for an annual average temperature increase of two to four degrees over the course of this century. This is caused not only by the geographical location, but also by the physical characteristics of the city. The spatial distribution of hot and cool areas is the result of spatially related planning processes. What options does spatial planning have in terms of its formal tools (development plan, land allocation plan, development concept), in order to minimise the consequences of increased thermal stress? Are these tools sufficient, in terms of the required adaptation measures, or is it necessary to supplement them with informal tools? What contribution can be made by associations, authorities or organisations, as well as by behaviour change? This thesis seeks to examine these questions critically and takes the spatial planning requirements from the point of view of climate research into account. The need to adapt to changing climatic conditions is not being questioned in scientific discourse, but it is still a novel topic in planning practice. What is certain is that adaptation will be an impulse for a gradually unfolding transformation process in forthcoming years, which will change the face of our cities. If one takes into account the durability of urban structures of around 100 years and the foreseeable intensification of the aforementioned effects until the middle of this century, it is now high time to integrate adaptation to these thermal changes into planning tools as an integral aspect as quickly as possible. The aim of the thesis in hand is to analyse whether current planning instruments are suitable to adapt to intensifying urban heat and to suggest further instruments where necessary. Eventually, the high quality of life has to be maintained in the future. In order to do so, a multiscalar application of planning instruments is necessary to bring the transformation process onto the right track.