The sky after rain

With the Sun at your back

After the rain stops, stand with the Sun behind you and a rainbow appears in the sky ahead. A rainbow needs two things. One is sunlight. The other is the countless raindrops floating in the sky. Let’s follow, step by step, the path sunlight takes through a raindrop to become a rainbow.

Why?A rainbow forms when raindrops send sunlight back toward you. That is why the Sun and the rainbow are always on opposite sides of the sky. You will never see a rainbow while looking toward the Sun.

Learn moreThe colors in this sky were not painted by hand. We calculated the angles of hundreds of thousands of light rays leaving raindrops, then painted the sky with how much light, and which colors, gather at each angle. The big number at the top is the key calculated value of each scene.

Where the rainbow sits

42°

Rainbow angle

about 42° (from the shadow point)

Sun height in this scene

15° above the horizon

calculated from the refractive index of water (IAPWS, 20 °C) and the laws of refraction and reflection