An understanding of the driving factors of urban heat islands could improve the urban thermal environment and provide planning strategies for sustainable urban/regional development. We selected Guangdong province in China as a case area, which covers 21 cities and more than 110 million people. We used multitemporal remote sensing data from multiple sources and socioeconomic statistical data to analyze the effects of various drivers of surface urban heat islands (SUHIs). The tested drivers

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... e urban agglomeration, physical indicators (e.g., vegetation and built-up indices), and socioeconomic indicators (e.g., population, gross domestic production, and nightlight intensity). The results show that physical indicators are determinants of daytime SUHIs whereas socioeconomic indicators are determinants of nighttime SUHIs, which indicates that daytime and nighttime SUHIs have different causal mechanisms in this region. Moreover, the results reveal that the influence of urban agglomeration on urban surface temperature is more significant at nighttime than in daytime, which implies that the warming effect of urban agglomeration is stronger at night. Together, the results indicate that joint control of urban size, urbanization level, and socioeconomic activities is crucial to alleviate SUHIs and safeguard sustainable development in this region. Index Terms-surface urban heat islands; driving factors; socioeconomic; nightlight data.