Why does the sky appear white sometimes?

The Earth’s atmosphere is made up of various substances, including dust particles, gas molecules, water droplets, ice crystals, and other hydrometeors. When solar radiation from the Sun reaches Earth's surface, it travels through multiple layers of the atmosphere, interacting with particles of varying sizes.

Some particles are smaller than the wavelength of light, while others are larger. Particles larger than the wavelength of light scatter incoming solar radiation. The scattering intensity of these particles is roughly the same for all wavelengths of white light, meaning it affects all colors equally. As a result, the light that reaches our eyes appears white, causing the sky to sometimes look white.

Note: The sky tends to appear whiter during hot days because the size of water droplets increases with the rise in temperature. As larger particles scatter light more uniformly across wavelengths, this causes the sky to appear white, especially on warmer days.