Cirrostratus clouds
![Cirrostratus clouds](/sites/default/files/media/images/cirrostratus1_big.jpg)
Anne Pharamond
Cirrostratus clouds are high, thin sheet-like thin clouds that usually cover the entire sky. The clouds are so thin that the Sun or moon can sometimes shine through and appear to have a halo as light hits the ice crystals and bends. The halo is the width of your hand held at arm's length. Cirrostratus clouds usually come 12 to 24 hours before a rain or snowstorm.