The principle of radiative cooling is to radiate the extra heat energy of Earth into outer space, and a lot of progress has been made in recent years. Radiative cooling is significantly affected by the air quality, and coolers reported at present only work well under a clear sky. Moreover, most of the world’s industrial cities are facing serious haze problems; thus improving the cooling performance under haze conditions needs to be addressed. We propose a water evaporation assisted radiative cooling technique, and the experimental results showed a remarkable subambient cooling of 6.4°C in daytime haze.