The term "Blue Moon" often refers to the second full moon in a calendar month. However, the full moon occurring on August 30, 2023, is not truly a Blue Moon in this sense. Instead, it is the third of four full moons in the astronomical (or seasonal) summer, a phenomenon sometimes called a "Seasonal Blue Moon" or "Blue Moon Season"** instead.

Since the lunar cycle is slightly longer than a calendar month (29.5 days vs. 30 or 31), it's possible for a month to have two full moons. The first one is called the "Regular Full Moon," and the second is commonly referred to as the "Blue Moon."

Astronomically, however, the term Blue Moon is not associated with any particular color change to the moon. Instead, it stems from an old Maine Farmers' Almanac tradition that dates back to the 1940s.

According to this almanac, the term Blue Moon initially meant the third of four full moons in a season that has four, rather than the more typical three. Over time, the concept of a Seasonal Blue Moon became mixed up with the perception of the moon turning bluish in color. Today, the term is often used to refer to the second full moon in a calendar month.