Despite the global uniformity of CO₂ increases, ocean surface temperatures respond unevenly, with pronounced regional differences in warming. In fact, the part of subtropical South Pacific Ocean, west of the coast of South America, is warming much more slowly, and in some cases, it’s even cooling. Our research shows that this delayed warming pattern can arise from increased rainfall over tropical South America. The released latent heat warms the upper troposphere, generating atmospheric wave response that travel westward and modulates the surface wind response over the subtropical Pacific. These winds further cool the ocean surface via evaporation. By using climate models, we found this cooling could happen within a few months of CO₂ increase and is mainly caused by fast changes within the atmosphere instead of slow processes in the ocean. This finding helps us understand how precipitation over land can affect nearby ocean surface temperatures, which is important for improving predictions of how global sea surface temperatures might change in a warming world.