AbstractThe purpose of this study is to examine the influences of mesoscale thermal and dynamical processes near land‐sea boundary on the formation and development of a squall line across the Hangzhou Bay (HZB) of East China Sea that resulted in strong surface winds and heavy rainfall. High‐resolution spatiotemporal analyses obtained from Variational Doppler Radar Analysis System via the assimilation of radar and surface observations are used for this study. We focus on meso‐scale factors leading to the initiation of the squall line and the development of a bow echo that caused damaging winds and heavy rainfall. It was found that a local‐scale sea breeze associated with the distinct coastline curvature of the HZB was pivotal to the formation of the squall line. The convective initiation occurred near the HZB's western coastline when the leading edge of the northeasterly sea breeze was met by a westerly outflow from a previous precipitation system to the west of HZB. After the formation of the squall line, a rear inflow jet descending from mid‐level to surface contributed to the formation of the bow echo and resulted in damaging local winds.