High temperature extremes (HTEs) have received increasing attention due to their rising impacts on human mortality, regional economies, and ecosystems. In this study, HTEs are defined as days with daily maximum temperature above the 90th percentile derived from a specific climatological period. Occurrences of summer HTEs in Southeast China (south of 35°N and east of 105°E) associated with atmospheric anomalies are investigated. Two key domains in the upper level that are associated with HTE variation, the “exit” and the “tail” of the East Asian Jet Stream (EAJS), are identified. Poleward displacement of the exit is associated with warming tropospheric temperatures over East Asia and tends to be linked with high HTE frequency, while enhancement of the tail is associated with cooling tropospheric temperatures in the northern Pacific and tends to be linked with low HTE frequency. A possible reflection effect of the stratosphere on cool summers in Southeast China is proposed. Furthermore, these two domains are in essence two sectors of the phase‐locked circumglobal teleconnection (CGT) pattern in the Northern Hemisphere. Linkages are found between HTEs in Southeast China and precipitation anomalies in the Indian summer monsoon region, and also in extratropical regions such as northeastern Europe. These teleconnections are set up through the CGT pattern associated with the westerly jet in the midlatitudes. These findings may be a source of variability and predictability of HTEs in Southeast China.

This study investigates summer high temperature extremes (HTEs) in southeast China and their linkage with the El Niño–Southern Oscillation (ENSO) and atmospheric circulations in the East Asian summer monsoon (EASM). An interdecadal change in HTEs associated with the abrupt shift of the ENSO–monsoon climate in the late 1980s is demonstrated. Before this interdecadal shift, the interannual variability of HTEs was linked mainly to temperature adjustments associated with the meridional displacement of the East Asian jet stream (EAJS), whereas after the shift HTEs were found to follow an ENSO cycle, which may be due to intensified and persistent ENSO activities, tropical Indian Ocean (TIO) warming, and changes in atmospheric teleconnections. Impacts of the EAJS, the South Asian high (SAH), and the western North Pacific subtropical high (WNPSH) on HTEs are further investigated based on empirical orthogonal function (EOF) analysis. It is found that mainly the first leading EOF mode with a homogeneous spatial pattern shows dominance before the interdecadal shift, whereas both of the first two leading EOF modes show dominance after the interdecadal shift. A possible mechanism of how HTEs in southeast China are linked to the EAJS, the SAH, and the WNPSH in the ENSO–monsoon coupled system is proposed.