A blood moon, which is a total lunar eclipse where the Moon appears reddish due to Earth's shadow, typically occurs about 2 to 4 times per year in total or partial form. However, total lunar eclipses that show the full "blood moon" effect happen roughly every 2 to 3 years from any specific location on Earth. The Moon often takes on a red color when it is fully eclipsed because Earth's atmosphere filters the sunlight reaching the Moon, scattering shorter blue wavelengths and allowing longer red wavelengths to illuminate it. Additionally, rare sequences of four total lunar eclipses (blood moons) in about two years, called lunar tetrads, happen multiple times per century but are not an annual event.
