A blue moon doesn’t actually appear blue in color – it refers to the occurrence of an extra full moon in a specific time period. There are two types of blue moons:
- Seasonal Blue Moon: The third full moon in a season with four full moons
- Monthly Blue Moon: The second full moon within a single calendar month
The term ‘blue moon’ originated from the Maine Farmers’ Almanac and has nothing to do with the moon’s color. However, the moon can appear blue in rare circumstances when specific-sized dust particles in the atmosphere scatter red light, such as after major forest fires or volcanic eruptions. These truly blue-colored moons are extremely rare and are not related to the calendar-based blue moon phenomenon.