Abstract: Using daily temperature data from 2,474 stations provided by the National Meteorological Information Center and ERA5 daily reanalysis for 1981–2023, this study compares the low-frequency (LF) characteristics and dynamical and thermodynamical mechanisms of regional extreme heat events (REHEs) across four subregions in eastern China. The results indicate that the summer daily maximum temperature in each subregion exhibits significant 10–30-day oscillations. The evolution of REHEs in all regions is influenced by Rossby wave trains propagating from northwest (or west) to southeast (or east) across the Eurasian continent. Additionally, South China is also affected by the teleconnection wave trains propagating westward in the low-latitude western Pacific, while the other three regions are influenced by East Asia–Pacific (EAP) teleconnection patterns propagating southwestward. Accompanied by the dispersion of LF Rossby wave energy from the eastern Atlantic in the mid-to-high latitudes, the eastern part of the mid-latitude North American continent, the western Atlantic in the mid-latitudes, and the mid-to-low latitude Atlantic toward the four subregions from south to north, respectively, a key LF circulation system (i.e. the LF continental high) that governs REHEs in each region has formed. The system is deeper in the northern three regions, especially Northeast China, while it is relatively shallower in South China, where the lower troposphere is influenced by coastal LF cyclonic circulations. The eastward and northward extension of the South Asian High notably affects the other three regions, especially South China, excepting for Northeast China. The westward and northward expansion of the Western Pacific Subtropical High strongly influences all four regions, particularly the Yangtze River Basin. Enhanced upper-level convergence and lower-level divergence induce strong subsidence, particularly over South China, resulting in the atmosphere adiabatic warming. Coupled with a drier atmosphere, reduced cloud cover, and increased incoming solar radiation, these factors exacerbate surface heating. Thermodynamic diagnostics indicate that horizontal temperature advection significantly contributes to warming in all regions except for South China, with a stronger effects on the northern regions. The vertical transport and diabatic heating play important roles during the mid-to-late and early-to-mid stages of REHEs development, respectively, especially in South China.