When Is the March 2021 Full Moon? The Worm, Sugar, Sap, Crow Crust Moon Explained

The next full moon will appear for about three days on Sunday March 28, appearing opposite the sun at 2:48PM EDT.

There are many names for the full moon in March, which the Maine Farmer's Almanac began publishing in the 1930s, according to NASA. These names can be traced back to Native American sources, among others.

Terms such as the Worm moon, Crust moon, Sugar moon all refer to the full moon in March and come from different tribes.

Usually, these names are linked to the transition from the winter season to the spring season and describe how nature signals this change in various ways.

The Sugar moon, or Sap moon, is so named because March marks the time of year when the sap of sugar maple trees begins to flow, and they can be tapped.

Northern U.S. tribes also called the March full moon the Crust moon because of the crusty appearance of snow as it begins to thaw during the day and refreeze at night. Some called it the Crow moon because of the cawing of crows at the end of winter,

The Worm moon is thought to get its name from tribes more to the south, because March is the time of year in which earthworms begin to appear in the soil as the ground thaws.

According to NASA, the reason this name comes from southern tribes is because glaciers in the northern parts of North America wiped out the native earthworms there.

The Old Farmer's Almanac notes there are a number of alternative March moon names that point to the appearance of certain animals around this time, including the Eagle moon and Goose moon.

Full moons occur when the moon is positioned opposite the sun in its monthly orbit around the Earth. This means that the light from the sun passes the Earth and fully illuminates the moon's surface from our perspective on the ground, making the moon appear as a bright, full circle.

The opposite of a full moon is a new moon, when the moon is again positioned opposite the sun, but this time on the other side of the Earth, so that it comes between us and sun. As a result, all the light from the sun is hitting the back of the moon, or the side that we cannot see. The side of the moon facing us gets no sunlight, making it appear dark in the sky.

Usually, a new moon does not block out sunlight even though it comes between the Earth and the sun, because its orbit around the Earth is slightly tilted. On rare occasions it does block the sun, and this is called a solar eclipse.

There is also the term "supermoon," coined by astrologer Richard Nolle in 1979, which refers to when a new or full moon is also at its closest point to Earth. According to NASA, in a typical year there can be 2 to 4 full supermoons in a row.

The closest full moon this year will take place May 26.

Full Moon
A full Moon on Penzance seafront on December 13, 2016 in Cornwall, England. Matt Cardy/Getty