Fog is formed by the condensation of water vapour on condensation nuclei that are always present in natural air. The most stable fogs occur when the surface is colder than the air above.

• 雾是由水蒸汽凝聚在天然大气中总是存在着的凝聚核上而形成的。当地表或水表面比上面的空气冷时,,就出现最稳定的雾。