BACKGROUND: Many studies have shown that various kinds of diseases were associated with the variation of ambient temperature. However, there's only a scrap of evidence paying attention to the link between temperature and skin diseases, and no relevant national research was performed in China. OBJECTIVE: This study aimed to quantify the effect of heat on skin diseases and identify the vulnerable populations and areas in China. METHODS: Daily meteorological data, air pollutant data and outpatient data were collected from in 18 sites of China during 2014-2018. A time-series study with distributed lag nonlinear model and multivariate meta-analysis was applied to analyze the site-specific and pooled associations between daily mean temperature and daily outpatient visits of skin diseases by using the data of warm season (from June to September). Stratified analysis by age, sex and climate zones and subtypes of skin diseases were also conducted. RESULTS: We found a positive linear relationship between the ambient temperature and risk of skin diseases, with a 1.25% (95%CI: 0.34%, 2.16%) increase of risk of outpatient visits for each 1 °C increase in daily mean temperature during the warm season. In general, groups aged 18-44 years, males and people living in temperate climate regions were more susceptible to high temperature. Immune dysfunction including dermatitis and eczema were heat-sensitive skin diseases. CONCLUSIONS: Our findings suggested that people should take notice of heat-related skin diseases and also provided some references about related health burden for strategy-makers. Targeted measures for vulnerable populations need to be taken to reduce disease burden, including monitoring and early warning systems, and sun-protection measures.