In myth and folklore the full moon of each month is given a name. In many cases the waxing moon and waning moon are also given names. There are many variations, but the following list gives the most widely known names:
The blue moonThe term "blue moon" traditionally referred to cases where a three month season had four full moons (instead of the usual three). A season is not defined as a calendar quarter in a year beginning on January 1 but as one quarter of a year measured from solstice to solstice. The third moon in the season is deemed "blue" instead of the fourth by almanacs because the full moons occurring closest to solstices and equinoxes already have traditional names. Since there are on the average 12.37 full moons in a year, a "blue moon" must occur on the average every 2.7 years.
Wet Moon/Dry MoonA wet moon (also called a Cheshire moon) is a lunar phase when the "horns" of the crescent moon point up at an angle, away from the horizon, so the moon's crescent takes on the appearance of a bowl or a smile. A wet moon occurs when the crescent moon is near the horizon at a point more or less directly above the sun's (invisible) position below the horizon.This in turn is determined by the earth's and moon's positions in their orbits, the inclination of these orbits relative one another and to the earth's axis, and observer's latitude on the earth.
The path of a dry moon (left) and wet moon (right).
Wet moons occur routinely in the tropics (where the sun and moon rise and set nearly vertically), and rarely in Polar Regions (where the sun and moon rise and set at a glancing angle or not at all).