Fog forms when air near the ground cools to its dew point, or when extra moisture is added until the air becomes saturated. At that point, water vapor condenses into tiny droplets suspended in the air, which is basically a cloud at ground level.

Quick Scoop

Common ways fog forms include:

  • Radiation fog: Ground loses heat on clear, calm nights, cooling the air above it.
  • Advection fog: Warm, moist air moves over a colder surface and cools.
  • Evaporation or steam fog: Water evaporates into colder air, then condenses.

Fog is most likely when humidity is high, winds are light, and temperatures drop enough for condensation to start.