A hypothetical representation of a literal Blue Moon (yes, those are real). A Literal Blue Moon is actually the rarest type of Lunar event; they only occur in a region that has experienced a major wildfire or a volcanic eruption. For example, Blue Moons were seen after Krakatoa's 1983 eruption and Mount St. Helens' 1980 eruption. Also, a "Lavender" Moon was seen during the September 1950 Alberta Muskeg Fires, wherever the sky was clear. Whenever a major smoke event is large enough to make the Sun appear to be blue or violet, there is bound to be a literal Blue Moon that night (assuming the sky is clear enough for it to be seen).