In-flight icing poses a serious safety risk for aircraft operating in cloud environments containing supercooled droplets at low temperatures. In this study, computational simulations are performed to examine ice accretion and the degradation effect on the aerodynamic performance of a foldable-wing UAV under varying cloud conditions. A validated computational model, benchmarked against experimental data, is employed for the analysis. The findings reveal that changes in cloud properties significantly alter both the ice accretion patterns and aerodynamic characteristics. Additionally, the extent of ice buildup and the total ice mass are shown to vary with specific flight and atmospheric conditions. These changes have a notable impact on lift and drag forces, which in turn can substantially reduce the UAV’s range and endurance during flight through icing conditions.