You never see a rainbow from directly overhead because the geometry requires looking away from the sun.

The longer version

The antisolar point, around which the bow is centred, always lies opposite the sun. When the sun is high, that point sits far below the horizon, so the whole arc is pushed out of sight and no rainbow can appear overhead.

Rainbows favour mornings and evenings, when the sun is low enough for the geometry to work at ground level. The rule also explains why a bow appears to retreat as an observer walks toward it: its position depends on the sun, not on the rain. Above roughly forty degrees of solar elevation, a ground-level bow becomes impossible.

Where this entry sits

These facts explore how light behaves and how human eyes turn it into the colors we see. Along the way you meet rainbows, prisms, mirrors, shadows, lasers, and optical tricks that fool our vision every day. The full list sits on the Color and Light page, where every entry is listed in order.