Often referred to as UFOs due their flying saucer shape, lenticular clouds are stationary lens-shaped clouds that form at high altitudes, normally aligned at right-angles to the wind direction. When stable moist air flows over a mountain or a range of mountains, a series of standing waves are often formed on the downwind side. If the temperature at the crest of the wave drops to the dew point, moisture in the air may condense to form lenticular clouds. Under certain conditions, long strings of lenticular clouds can form, creating a formation known as a wave cloud. The wave systems cause large vertical air movements and so enough water vapor may condense to produce precipitation.

Since lenticular clouds generally do not form over low-lying or flat terrain, most people have never seen one and are not aware clouds with that shape can exist. Bright colors (called irisation) are sometimes seen along the edge of lenticular clouds. These clouds have also been known to form in cases where a mountain does not exist, but rather as the result of shear winds created by a front.