Question

when the humidity is high and temperature is low fog often forms why?

Answer 1

Fog begins to form when water vapor condenses into tiny liquid water droplets suspended in the air. This occurs from either added moisture in the air, or falling ambient air temperature. However, fog can form at lower humidities, and can sometimes fail to form with relative humidity at 100%

Answer 2

The moisture in atmosphere is called humidity. when the humidity becomes high and temperature is low the moisture starts to condensed and hence fog often forms