In Shenzhen, a short-lived rainstorm accompanied by gale occurred on 11 Apri1 2019, while a weak stable precipitation event happened on 11 Apri1 2020. The two distinct rainfall events take place in the similar circulation backgrounds of upper-level trough and lower-level shear. The features and associated mechanisms of the two events in the early rainy season are analyzed by using ERA5 reanalysis data. The short-lived rainstorm in 2019 comes along with a typical mesoscale convective system (MCS) , which migrates eastwards and leads to the short-time torrential rain and thunderstorm gale in Shenzhen. The MCS is triggered by the boundary layer convergence line, and then develops in good convective conditions of temperature and humidity and divergence at upper level, but unfavorable dynamic conditions such as weak convergence at lower level. In contrast, Shenzhen sees a much more tender and stable rain in 2020, which happens in the beneficial dynamic conditions of lower-level convergence but weak convective conditions. The comparison suggests the convective conditions such as temperature and humidity play more important role than dynamic conditions in the development of MCSs in the early rainy season of South China. The Q-vector shows significant convergence over Pearl River Delta areas such as Shenzhen up to12 h in advance of the strong convection,which is a skillful precursor for the occurrence of MCS and convection.