INTRODUCTION: Heat exposure and heatwaves are becoming more frequent and prolonged due to global warming. Heat exposure poses a significant potential risk for respiratory diseases. However, a comprehensive synthesis of existing evidence on the health impacts of heat exposure on respiratory diseases is lacking. This review aims to address this knowledge gap. METHODS: The PubMed, Scopus, Embase, and Web of Science databases were searched for reviews examining the impact of heat exposure on respiratory-related mortality and morbidity, as well as on respiratory diseases such as asthma, pneumonia, COPD, acute bronchiolitis, and acute respiratory infections. The final search was conducted in July 2024. The quality of evidence for each health outcome category was assessed using a modified GRADE framework. RESULTS: A total of 28 reviews were included. There is strong evidence linking heat exposure to increased mortality in respiratory diseases. However, the associations between heat exposure and respiratory morbidity are less robust. Asthma is the most studied condition and has the most consistent evidence supporting its association with heat exposure. For other respiratory diseases, the evidence remains inconclusive. CONCLUSION: This review strengthens the evidence that heat exposure increases the risk of respiratory diseases globally. Future research should focus on low-income countries, specific respiratory diseases, and the integration of multi-dimensional data to develop evidence-based prevention and adaptation strategies.