Our atmosphere contains atoms and molecules of different sizes. According to their sizes, they are able to scatter different wavelength of light. It acts as a scattering center for light other frequencies which are lower than the frequency of blue light. In a hot day due to rise in temperature, water vapor into the atmosphere which leads to abundant presence of water molecules in atmosphere. These water molecules scatter the colors of other frequencies (other than blue). All such colors of other frequencies reaches our eye and white color appeared to us.