In recent years, road accidents due to heavy rainfall have become an alarming issue that needs to be researched. In this regard, a comparative study is performed from the aerodynamic perspective to observe the flow phenomena alteration around a generic hatchback ground vehicle. The analysis deals with a 75% scaled wing-attached Ahmed body where NACA 0018 airfoil profile is chosen for the wing profile. All the possible combinations are compared initially by the RANS-based k-epsilon turbulence model at a Reynolds number 2.7×106. Later, the instantaneous flow phenomenon is analyzed with the LES formulations. The simulation results imply an 11–12% average increase in the drag coefficients for with and without wing conditions and a decrease in lift coefficients by 24% for the wing-attached state. Besides this, shifts in the critical drag and lift coefficients' slant position from 25° to 15° in the wing-attached normal state and 12.5° in the wing-attached rain state are noticed. The careful inspection of different vortex formations, merging, energy distribution associated with the eddies, and pressure coefficient variations reveal the tentative reasons for the aerodynamic penalties. Also, the instantaneous flow analysis discovers an additional recirculation region for the wing-attached condition. This study will assist in obtaining a distinct picture of the aerodynamic penalties faced by a hatchback ground vehicle under heavy rain conditions and finding the role of a rear wing in overcoming adverse weather conditions.