Halos, sun dogs, double rainbows and the green flash: what sunlight and moonlight draw in ice crystals, water droplets and the air itself, and where to look for each.
Drawn by ice crystals
Drawn by water droplets
- Double rainbowTwo bows of colour opposite the Sun, the outer one fainter and with its colours in reverse order.
- Iridescent cloudSoft patches of pink, green and blue on the thin edge of a cloud near the Sun.
- GlorySmall coloured rings around your own shadow on a cloud or fog below you, opposite the Sun.
Drawn by the air itself
- Crepuscular raysBeams of light and shadow fanning out from the hidden Sun, made visible by haze in the air.
- Red skyClouds glowing red and orange at sunrise or sunset, lit from below by light that crossed a long path of air.
- Green flashA green spark on the top of the Sun for a second or two, just as it sets or rises over a clear horizon.
Bending Light Through Crystals
Ice crystals in high clouds act as tiny prisms. They refract sunlight to create geometric shapes. A halo often appears as a ring around the sun or moon.
You may see two sun dogs on either side of this ring. These bright spots form when light passes through hexagonal plates. The effect requires clear air and thin cirrostratus clouds.
Look upward when the sky feels milky but still lets light through.
Scattering and Reflection
Water droplets scatter and reflect light differently than ice. Crepuscular rays appear as beams radiating from cloud gaps. Iridescent clouds show pastel colors near the sun’s position.
Double rainbows occur after showers when sunlight hits falling drops. The outer bow shows reversed colors. Red skies happen at dawn or dusk due to long atmospheric paths.
This scattering removes blue wavelengths. The green flash is brief and hard to catch. It appears at the horizon during sunset if visibility is perfect.
Viewing Angles and Conditions
A glory forms directly opposite the sun. You might see it from an airplane looking down on clouds. It looks like a colored ring around your shadow.
Each phenomenon needs specific alignment. Do not expect them every day. Watch for changes in cloud texture and sun angle.
Patience helps you notice these fleeting optical events. Keep your eyes open for subtle shifts in color and shape. The sky offers quiet visual rewards for attentive observers.