We study how temperature exposure affects mental health in a developing country using data from China Family Panel Studies (CFPS). We find that exposure to high temperatures leads to worse mental health. Specifically, one additional day above 27 °C during the past week would increase individuals' total CESD 8 score by 1.5%, and the likelihood of having severe mental illness by 6.2% relative to a day in the reference temperature bin. We further estimate the potential mitigating effects of air conditioning on the relationship between temperature and mental health. We find that the identified relationship is mitigated by installing air conditioning. We also test some mechanisms through which temperature might impact mental health, including physical health status and sleep. We further discuss the overall health expenditure burden associated with climate change.