Thermal Environment Characteristics of Local Climate Zones Based on Summer Stage Subdivision: An Observational Study in Shenyang, China

Global warming and urbanization have exacerbated the urban heat island (UHI) effect, threatening human settlements and public health. Existing studies have primarily focused on analyzing urban thermal environment characteristics throughout the year or in specific seasons; however, research examining the urban thermal environment at different stages within a season is scarce. This study employed Local Climate Zone (LCZ) classification and focused on Shenyang, a representative city in China’s severe cold regions. Based on field measurements and multi-source meteorological data, we investigated the differences in thermal environment across seven LCZs throughout summer and at different summer stages. The result show that the UHI effect in Shenyang significantly intensified at nighttime and weakened during the daytime. Built-type LCZs 2 and 4 exhibited the highest nighttime urban heat island intensities (UHIIs), with maximum values of 7.6 °C and 5.4 °C, respectively. The duration of the daytime urban cold island effect in built-type LCZs increased significantly in mid-summer and late-summer. Land cover-type LCZ A exhibited the urban cold island effect only during the daytime throughout the summer. The UHII remained relatively stable across all LCZs during mid-summer. This study provides empirical support for developing targeted heat risk mitigation strategies for cities in severe cold regions.