The Next Full Moon is the Buck Moon, Thunder Moon, Hay Moon or Mead Moon and it happens at 10:37pm.

The next full Moon will be tonight, Friday night, July 23, 2021, appearing opposite the Sun in Earth-based longitude at 10:37 p.m. EDT. While this will be on Friday for most of the Americas, from Newfoundland and Greenland eastward to the International Dateline this will be on Saturday, July 24, 2021. Many almanacs and commercial calendars are based on Coordinated Universal Time (UTC) and will show this full Moon on Saturday. The Moon will appear full for about three days around the peak of the full Moon, from Thursday evening through Sunday morning.

What’s in a name

The Maine Farmer’s Almanac first published Native American names for the full Moons in the 1930s. According to this almanac, as the full Moon in July – the Algonquin tribes in what is now the northeastern United States called this full Moon the Buck Moon. Early summer is normally when the new antlers of buck deer push out of their foreheads in coatings of velvety fur. They also called this the Thunder Moon because of early Summer’s frequent thunderstorms.

Europeans called this the Hay Moon for the haymaking in June and July, and sometimes the Mead Moon (although this name and “Honey Moon” were also used for the previous full Moon). Mead is created by fermenting honey mixed with water, sometimes adding fruits, spices, grains, or hops.

For Hindus, Buddhists, and Jains, this is the Guru Full Moon (Guru Purnima), celebrated as a time for clearing the mind and honoring the guru or spiritual master.

For Theravada Buddhists, this full Moon is Asalha Puha, also known as Dharma Day or Esala Poya, an important festival celebrating Buddha’s first sermon. As the full Moon day of Waso (the fourth month of the traditional Burmese lunisolar calendar), this is the start of the three-month annual Buddhist retreat called Vassa.

The Moon and calendars

In many traditional lunisolar calendars, full Moons fall in the middle of the lunar months. This full Moon is in the middle of the sixth month of the Chinese calendar and Av in the Hebrew calendar, corresponding with Tu B’Av, a holiday in modern Israel similar to Valentine’s Day.

In the Islamic calendar, the months start with the first sighting of the waxing crescent Moon shortly after the New Moon. This full Moon is near the middle of Dhu al-Hijjah, the 12th and final month of the Islamic year. Dhu al-Hijjah is the month of the Hajj, the Festival of the Sacrifice, and is one of four sacred months during which fighting is forbidden.

(Tobias Hartl/dpa via AP)

Since this is the Thunder Moon, a quick note on lightning safety. Most of the lightning that strikes the ground arcs from the negatively charged bottom of the storm to the ground underneath the storm. Much rarer is positive lightning, which arcs from the top of a thunderstorm to strike the ground up to eight miles away. Positive lightning can sometimes strike areas where the sky is clear (hence the term “bolt out of the blue”). Because it arcs across a greater distance it tends to be 5 to 10 times more powerful than regular ground strikes. Because it can strike dry areas outside of the storm, positive lightning tends to start more fires than negative lightning. Although positive lightning is rare (less than 5% of all lightning strikes), the lack of warning combined with its greater power tends to make it more lethal. A good rule to follow is, if you can hear the thunder, you can be struck by the lightning.

As usual, the wearing of suitably celebratory celestial attire is encouraged in honor of the full Moon. Be safe (especially during thunderstorms), avoid starting wars, and take a moment to clear your mind.