What Is a Moonbow in Yosemite
A moonbow, or lunar rainbow, is a rainbow produced by moonlight rather than sunlight. In Yosemite National Park, moonbows typically form when the moon is bright, low in the sky, and shining on water droplets from waterfalls such as Yosemite Falls, Bridalveil Fall, or Vernal Fall. The park's geography and frequent mist create ideal conditions for these rare nighttime rainbows.
Moonbows are much fainter than solar rainbows because moonlight is less intense. Human eyes also struggle with color perception in low light, so moonbows often appear white to the naked eye. Long-exposure photography reveals their spectral colors, and park rangers note that clear skies, high waterfall flow, and a moon elevation below about 42 degrees increase the chance of visibility.
Best Time and Conditions to See Moonbows in Yosemite
Moonbows are most likely during the spring and early summer months when waterfall flows are high, typically from April through June. Peak conditions often align with full or near-full moon phases on clear nights with low wind, and rangers recommend checking waterfall discharge data and lunar phases before planning a visit.
Key Viewing Locations
Popular spots include the mist trail near Vernal Fall, the base of Bridalveil Fall, and areas along the Merced River where spray is heavy. The park service advises arriving before full darkness, using red-light headlamps to preserve night vision, and staying on designated trails for safety.
Planning a Moonbow Viewing Trip to Yosemite
Visitors should monitor park alerts, waterfall conditions, and moonrise times through official Yosemite National Park channels. Permits may be required for overnight stays or certain trailhead parking, and the park's reservation system can fill quickly during peak seasons.
Photography and Equipment Tips
A tripod, camera capable of long exposures, and a remote shutter release help capture moonbow colors. Park rules prohibit drones in most areas, and photographers should use headlamps with red filters to avoid disrupting other visitors' night vision.