Worldwide rainbow forecast
Know when the light will bend.
Bowcast reads a 40 member weather ensemble through the optics of how rainbows actually form: sunlit rain, with the sun below 42 degrees, seen from the right angle. It predicts the chance of a rainbow, hour by hour, seven days out, anywhere on Earth.
The physics, honestly
A rainbow needs three things to line up at once.
Rain in front, sun behind
There has to be falling rain in one part of the sky and clear sun in the other. Bowcast checks both across the ensemble.
The geometry of the bow
A rainbow only forms when the sun sits lower than 42 degrees above the horizon, so timing near sunrise and sunset matters most.
Looking the right way
The bow appears opposite the sun, centered on your antisolar point. Bowcast tells you which way to face.
The app is the almanac, made live.
The same reading you see here is the reading on the map, on the live board, and on every city page. Glance to learn whether, where, and when to look. Reveal the model when you want the evidence.