The weather research and forecasting(WRF) model, coupled with a multi-layer urban canopy model BEP(building energy parameterization), is used to investigate a high temperature episode occurred in the Yangtze River Delta region on 13 August 2013.A southeasterly breeze, consistent with the direction of Suzhou-Wuxi-Changzhou urban cluster, is prevailed over the Yangtze River Delta region during the episode.Simulating results show that significant urban heat island(UHI) effects occur in the urban cluster, and the UHI intensity increases from Suzhou to Changzhou.Under the impact of the southeasterly breeze, the UHI effects of the three individual cities merge together, forming a stronger UHI circulation.In the night, the UHI circulation is weakened by the stable planetary boundary layer, which is favorable for the downstream transport of the UHI effect.The urban planetary boundary layer height is significantly increased by the UHI effect.During the daytime, a strong lake breeze between Lake Taihu and land has great impacts on the UHI of the nearby cities.Air temperature over Wuxi and Changzhou is significantly decreased by the cold air from Lake Taihu, and the upward extension of the UHIs over the two cities are suppressed.Connections of the UHIs between Wuxi and Changzhou are weakened by Lake Taihu.The planetary boundary layer height over Wuxi and Changzhou is more significantly decreased by the lake breeze during daytime.