A dense, chemical-smelling fog across the US, Canada, and UK triggered panic, respiratory symptoms, and conspiracy theories.

Fog arises when the temperature is lowered to the dew point, or enough moisture is added to raise the dew point, and by mixing cold air with warm, moist air. The various types of fog each have ...

But why? Here's what's causing the latest bout of fog: There are a handful of different types of fog with varying characteristics, according to the weather service. "Radiation fog" forms ...

People reported a persistent "toxic fog" across the U.S. and other areas. The phenomenon may be more benign, though.

Fog, especially when dense, can pose significant risks to drivers. It contributes to numerous accidents annually and can disrupt air travel by affecting visibility during takeoff and landing.