The facts about smog, fog and haze
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Fog is formed from water droplets or ice crystals suspended in the air at or near Earth’s surface, while haze is an atmospheric phenomenon where dust, smoke and other dry particles obscure the sky.
The international definition of fog is visibility of less than a kilometer, whereas haze reduces visibility from 2 to 5 kilometers.
In fog, relative humidity exceeds 90 percent, while that of haze is below 80 percent.
The thickness of a fog can range from tens of meters to about 200 meters, whereas it’s 1 to 3 kilometers for haze.
A foggy zone has an obvious boundary, but areas of haze have no such boundary.
Fog often appears at night or dawn, while haze can occur at any time.
Smog is fog or haze combined with smoke and other pollutants.
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