Mist or haze?
The term 'mist' is used when the visibility is 1 km or more, the relative humidity 95% or more and the atmospheric obscurity caused by suspended microscopic water droplets or wet hygroscopic particles. The term 'haze' is used, whatever the horizontal visibility, when the relative humidity is less than 95% and visibility is reduced by the very small, dry, solid particles suspended in the atmosphere.

  Fog warnings
The sound of a lighthouse foghorn can be heard about 30 km (20 m) over water. Fog is also known as 'clouds on the ground'. Fog can consist of minute ice crystals rather than water droplets - this is called ice fog.