Natural light is even more varied when the conditions in the atmosphere change. There are innumerable patterns of cloud cover, and not only do they alter the appearance of the sky itself, but they also filter, diffuse and reflect the light from the sun. Clouds, in all their forms, are made up of water droplets, which are too large to scatter light wavelengths selectively. Instead, water droplets scatter over the entire spectrum, and cause clouds to appear white or gray. Clouds act as reflectors and, at sunrise and sunset, are responsible for dramatic color effects.
A thin haze of cloud coverage reflects sunlight as more white than blue and softens shadow edges . As cloud cover increases, the sun's light is diffused over a larger and larger area until, on a completely overcast day, the entire sky is the light source and there are practically no shadows at all. This flat lighting gives poor modeling, but can be very effective for complex shapes and gives faithful colors. A highly detailed garden, for example, might look clearer in such light.
In extreme weather conditions, such as the falling snow and heavy rain, both contrast and colors are subdued and subtle. At times, even impressionistic results are possible.
