The study investigates the urban heat island (UHI) effect in 32 major Chinese cities using MODIS data from 2002 to 2012. The results show that the UHI effect decays exponentially toward rural areas for most of the cities, with a significant "cliff" in temperature between urban and rural regions. The footprint of the UHI effect (FP), which includes the urban area, is estimated to be 2.3 and 3.9 times the urban size during the day and night, respectively, with large spatiotemporal heterogeneities. The study highlights that ignoring the FP can underestimate the UHI intensity and alter its direction in some cities. The findings provide new insights into the characteristics of the UHI effect and emphasize the importance of considering city- and time-specific FP when assessing the urbanization effects on local climate.The study investigates the urban heat island (UHI) effect in 32 major Chinese cities using MODIS data from 2002 to 2012. The results show that the UHI effect decays exponentially toward rural areas for most of the cities, with a significant "cliff" in temperature between urban and rural regions. The footprint of the UHI effect (FP), which includes the urban area, is estimated to be 2.3 and 3.9 times the urban size during the day and night, respectively, with large spatiotemporal heterogeneities. The study highlights that ignoring the FP can underestimate the UHI intensity and alter its direction in some cities. The findings provide new insights into the characteristics of the UHI effect and emphasize the importance of considering city- and time-specific FP when assessing the urbanization effects on local climate.