The full moon that occurs in June is popularly known as the Strawberry Moon, appearing to have a warm, reddish, or amber hue. This visual phenomenon is not caused by any physical change to the moon itself. The striking color is an optical effect created entirely by the Earth’s atmosphere acting as a filter. This atmospheric effect combines with the moon’s specific path across the sky during the summer season to produce the noticeable color shift. Understanding this requires exploring both the historical context of the name and the fundamental physics of light scattering.
Where the Name Strawberry Moon Comes From
The name “Strawberry Moon” has its roots in the traditions of North American Native American tribes. It was used by the Algonquin, Ojibwe, Dakota, and others to mark the timing of the annual harvest of wild strawberries. This full moon, typically the last of spring or the first of summer, signaled the short window when the berries ripened and were ready for gathering.
The name serves as a seasonal marker, indicating a time of abundance and harvest rather than describing the moon’s appearance. Other tribes used different names based on local events. For instance, this same moon is also known regionally as the Rose Moon, the Hot Moon, or the Green Corn Moon, reflecting the diverse agricultural and climatic markers across different indigenous groups.
The Physics of Red Light
The mechanism that causes the moon to appear red is the same one responsible for the orange and red colors seen during sunrises and sunsets. This effect is explained by a process called Rayleigh scattering, which describes how light interacts with tiny particles in the atmosphere. Light is composed of different colors, each corresponding to a different wavelength.
Shorter wavelengths of light, like blue and violet, are scattered much more easily by the Earth’s small atmospheric gas molecules than the longer wavelengths, such as red and orange. When the moon is high overhead, the light has a short distance to travel through the atmosphere, allowing all colors to reach the eye. As a celestial body dips closer to the horizon, its light must pass through a significantly thicker layer of the atmosphere.
This long path through the air causes most of the blue and green light to be scattered away, leaving only the less-scattered, longer-wavelength red and orange light to travel directly toward the observer’s eyes. The moon is left with a warm, reddish tint. The exact shade of red or amber depends on the amount of dust, pollution, or moisture present in the atmosphere at that moment.
Why This Phenomenon Happens During the June Full Moon
The Strawberry Moon’s tendency to look redder is a direct consequence of its orbital path, which is tied to the Summer Solstice in the Northern Hemisphere. The full moon always rises nearly opposite the sun in the sky. Since the June Solstice marks the point when the sun is at its highest altitude of the year, the full moon occurring around that time must take the opposite, lowest path across the sky.
For observers, the June full moon tracks very low above the horizon. Because the moon spends more time at a low angle, its reflected light consistently travels through a greater volume of the Earth’s atmosphere. This extended journey maximizes the effects of Rayleigh scattering, intensifying the reddish-orange appearance, particularly during moonrise and moonset. The perceived redness is therefore a predictable annual event, a beautiful illustration of how celestial mechanics and atmospheric physics intersect.