There is an idiom for raining hard: It's raining cats and dogs. But is there an idiom for snowing hard?
If it is snowing so much one can not see beyond one's arm, it is called
No, there is no equivalent idiom.
All day it was raining cats and dogs. That night it snowed heavily.
Snowfall intensity is rated by visibility (mild, moderate, heavy), and snowfall patterns can be described with words like "flurries," or "a blizzard."
Fallen snow can metaphorically become a blanket or be blanketing objects or the landscape: "A thick blanket of snow covered the forest." In general this is fallen snow on the ground, not snowfall in the air -- although fog can also "blanket", and a weatherman / meteorologist can describe snowfall blanketing a geographic region.