This year, for the first time since 1944, the entire world will experience a blue moon on Halloween. While there was a blue moon during the 2001 holiday, only people in the Central and Pacific time zones witnessed it. However, the entire world will experience a full blue moon on October 31 this year. The moon appears blue when many particles of at least 90 nanometers in size are present in the atmosphere. These particles block out red and yellow light, creating this extremely rare visual phenomenon.

Every month except for February can have a blue moon due to the 29-day lunar cycle. In a month with two full moons, the first full moon is normally a harvest moon that appears either in the first days of the month, while the second full moon, known as a blue moon, appears in the last days. The term harvest moon originated from farmers who harvested their crops in the bright early evening moonlight, while the blue moon got its name from the 16th century phrase,”once in a blue moon,” due to the rarity of the occurrence.

This Halloween, the full blue moon will add to the spooky, fun-filled atmosphere of the holiday, as it shines on people across the world.

For more information, visit:

• Where did the Term Blue Moon Come From?
• What is the Harvest Moon?
• What is a blue moon and how often does it occur?
• What is a Blue Moon?
• Blue Moon-Britannica