Weather Tidbits: Radiation Fog

This edition of Weather Tidbits will be discussing radiation fog. Radiation fog is very common during autumn mornings, and requires certain conditions to form. First, the sky should be clear. When the sky is clear during the overnight, that allows all the heat accumulated during the day to efficiently escape into the atmosphere. If there are too many clouds, the surface is insulated and, therefore, cooling is not as efficient. Secondly, the winds must be calm. If there is too much wind, the air will mix out and fog is much harder to form as a result. With these conditions, the temperature can then cool down to the dew point temperature. When this happens, the air becomes saturated, meaning the air cannot hold any more water. Because of this, water condenses out in the form of fog.