The pseudo-global warming (PGW) method is widely used to examine climate-change impacts on heavy rainfall. However, the thermodynamic variables selected as climate deltas in PGW experiments often differ among studies and are determined subjectively. This study investigates how different selections and combinations of climate deltas influence simulated thermodynamic and dynamic fields, using a heavy rainfall event associated with a mesoscale convective system (MCS) as a case study. We conducted PGW sensitivity experiments with the Weather Research and Forecasting (WRF) model by applying climate deltas for air temperature (T), sea surface temperature (SST), and relative humidity (RH), individually and in combination, based on climate projections. MCS precipitation was sensitive to the applied thermodynamic perturbations. The T delta increased atmospheric water vapor, raising basin-averaged accumulated precipitation by a factor of 1.62 relative to the control simulation. The SST delta increased surface heat fluxes and enhanced atmospheric instability, whereas the RH delta caused no substantial thermal changes. The SST and RH deltas shifted the heavy rainfall areas associated with the MCS, producing large changes in basin-scale precipitation. These results indicate that climate-delta selection can modify mesoscale dynamics and represents an important source of uncertainty in PGW experiments.