A streak of light in the night sky so bright that it can cast noticeable shadows. Due to the hazard the National Weather Service issues flash flood watches and flash flood warnings. A flash flood is rapid flooding that occurs during or within a few hours of an intense rain. A flood develops gradually, many hours or even days after the rain event. The name originated in the Alps.
Fog is literally a cloud on the ground.
A fairly well-defined mass of fog observed at a distance, most commonly at sea or over a very large lake. A light breeze that blows from forests toward open country on clear calm nights. Fresh snow is an excellent insulator. In cold climates, the annual spring rise of streams as a result of melting snow. The transition zone between two different air masses.