Abstract Extreme heatwaves will occur more frequently and with higher intensity in future. Their consequences for human health can be fatal if adaptation measures will not be taken. This study analyses factors related to heat adaptation measures in private households in Germany. During the summer months of 2019, indoor temperatures were measured in over 500 private households in the City of Augsburg, Germany, accompanied by a survey to find out about heat perception and adaptation measures. Hypotheses deducted from the Protective Action Decision Model were tested using one-way ANOVAs, regression analysis and in the end a multiple hierarchical regression model. The results of the hypotheses tested imply an influence of knowledge and heat risk perception of heat adaptation behaviour and an influence of age on heat risk perception. The results of the regression model show an influence of the efficacy-related attribute, of age, indoor temperature, subjective heat stress and health implications to heat adaptation behaviour. In the end, this study proposes adjustments to the PADM according to the results of the hierarchical regression analysis.