Cloudspotters yearn for spotting the rare optical effect known as a rainbow wheel. This is a wheel formed by the arc of a rainbow that has beams of light and shade within it, emanating from the centre like the spokes of a wagon wheel.

To see any rainbow, you need direct sunlight shining from behind onto a rain shower up ahead. For the bow to contain spokes of light and shade, like this one spotted by CloudSpotter app user 'kmgoslin' over Essex Junction, Chittenden County, Vermont, US, you need also for tall clouds on the horizon behind to cast shadows right across the whole sky. The effect of perspective causes the parallel beams of light and shade from the cloud shadows to converge on the antisolar point, which is always at the middle of the rainbow.

A cloudspotter’s bucket list doesn’t depend on crossing the world in search of the extraordinary. It’s about finding what’s extraordinary in the everyday.