The realtime altitude fields, ECMWF nest grid data at 12UTC and NCEP reanalysis data are used to analyze the extreme heat process from August 6 to 10 in 2013 along the north shore of the Hangzhou Bay. The results show that the largescale circulation background of the persistent extreme high temperature (40 ℃) weather include the subtropical ridge steadily at 30°N, divergence at upper levels, 26 ℃ warm air mass at lower levels under the strong subtropical high center. The subtropical high extended westwards and the South Asia high moved eastwards, which produced a profound secondary circulation loop in the vertical direction, which was an important reason for the extreme high temperature lasted longer and wider. The emergence of extreme heat was closely related with the exceptionally dry air. The reasons for more extreme temperature records have been broken along the north shore of the Hangzhou Bay are: those highlevel dry air superimposed on the southward lowerlevel subtropical dry warm mass, the adiabatic heating effect of sinking airflow from top to ground, and the warm advection at lower levels. The prediction verification of four major numerical models for high temperature service indicates: the error of EC model prediction is small and stable, about 1 ℃, and the errors of GFS, JMA, and T639 are 3, 4, and 5 ℃, respectively, which need to correct in service. These results can be used as references in the summer high temperature forecast.