A “blood moon” is actually not an astronomy term, the almanac said. Instead, it is a popular phrase for a total lunar eclipse, so called because the moon takes on a brown or reddish glow.
This happens because some sunlight does reach the moon, but it is bent and filtered by the Earth’s atmosphere, giving it a brown or reddish color, according to NASA. The exact color depends on the “sooty-ness” of the atmosphere, including among other things how recently volcanoes have erupted, how many clouds there are and how much pollution there is around the globe.
“Flower moon” is also not an astronomical term. Instead, the Old Farmer’s Almanac attributed the name to the Algonquin peoples, and said that it refers to the flowers opening across North America this month.
The almanac added that the name traditionally applies to the entire month, not just the full moon.