The uncertainty of climate projection is significantly contributed by warm cloud feedback, which involves a complex interplay of various mechanisms. However, it is hard to unentangle temperature’s impact on a single cloud with experiments, since the cloud dynamics always covaries with environmental thermodynamical conditions. In this study, we investigate a simulated single shallow cumulus cloud’s response to temperature using two perturbation methods, namely “uniform” and “buoyancy-fixed”, the latter of which keeps the buoyancy profile unchanged in temperature perturbation. High-resolution large eddy simulation shows that uniform warming significantly increases cloud buoyancy, reducing cloud adiabaticity. If buoyancy is fixed, warming only reduces cloud area, leaving adiabatic fraction almost unchanged. Such response can be explained by Clausius-Clapeyron effect with an idealized 1D diffusion model, showing that warming increases the cloud-environment absolute humidity difference more than the increase in cloud liquid water content, resulting in a faster loss in both cloud coverage and total liquid water solely by lateral mixing. The responses of cloud coverage and total liquid water counteract, making adiabatic fraction insensitive to temperature change. Our works shows that cloud adiabatic fraction’s response to temperature is sensitive to the perturbed structure of the boundary layer, and the cloud coverage reduction by diffusion acts as positive cloud feedback mechanism in addition to the adjustment processes of the boundary layer.