With 37 days of high temperature and several new historical records, high temperature weather of Jiaxing in 2003 could be encountered once every 50 years no matter in duration or intensity. It shows that this resulted from remarkably strong west-Pacific Subtropic High in Jul. and Aug. and comparatively weak eddy intensity and west-wind circulation index. It's also a certain result of the climate warming. Outcome of wavelet analysis: high temp. has main periods of respectively 16- and 8- year and there was a quasi-2- year surge since 2001.