Low visibility during cold weather is due to:

During cold weather, water droplets instead of moving up at a higher altitude stays near the earth’s surface and cause fog. Along with this, a lot of vehicular emissions and smoke from industries include unburnt carbon and hydrocarbons, these particles gets mixed with the already suspended fog and lead to the formation of smog. This smog suspends closer to the surface of earth causing visibility issues along with nasal congestions and other nasal infections.