Cirrostratus
16,500 - 40,000 ft (5,000 - 12,000 m)
“A ring around the moon means rain will come soon”— Traditional weather lore
Cirrostratus is the subtle one, the cloud that makes you wonder if there's a cloud at all or if someone just turned down the brightness on the sky. It forms a thin, milky veil so high up that it can cover the entire celestial dome while barely announcing its presence.
The telltale sign of cirrostratus is the halo—a ring of light around the sun or moon that appears when light refracts through millions of hexagonal ice crystals. If you spot a halo, you're looking at cirrostratus, even if the cloud itself seems invisible.
These sheets of ice crystals are often the advance guard of an approaching warm front, sliding in silently to prepare the sky for the weather changes to follow. They're the opening act, the quiet setup before the main event.
things worth knowing
- Halos appear at exactly 22 degrees from the sun or moon due to the hexagonal structure of ice crystals
- Cirrostratus can cover thousands of square miles while remaining nearly invisible
- The veil is so thin that shadows remain sharp on the ground below
- Ancient sailors used halos to predict storms with remarkable accuracy
weather wisdom
Strong indicator of approaching precipitation within 12-24 hours