Yesterday's high temperature in Florianópolis, Brazil, topped 90 degrees F, typical of the region's warm summer days.
Nevertheless, when Cristiano Andujar looked up from the steps of the City Cathedral, he saw definite signs of freezing air. “There were two beautiful ice halos around the sun,” he says. “People on the sidewalk were stopping and pointing.”
In this photo, which Andujar took, the big ring around the sun is a common 22-degree halo, caused by sunlight shining through hexagonal ice crystals in cirrus clouds. Floating almost 10 km high, these clouds were freezing despite scorching temperatures on the streets of Florianópolis.
Just below the 22-degree halo, Andujar’s camera captured an intensely colorful band of light called a circumhorizon arc, also caused by ice crystals in the clouds. Summer is the season for circumhorizon arcs because they appear only when the sun is high in the sky–more than 58o above the horizon. The arc’s enormous size and pure spectral colors make it one of the most beautiful of all ice halos.
Are you sweating under a summer sun? Look up anyway. You might see something very cool.
Gallery: Spaceweather Gallery