The window panes were covered with frost...

Photo courtesy of PublicDomainPictures.net

An excerpt:

     The snow kept coming till it was drifted and banked against the house.  In the mornings the window panes were covered with frost in beautiful pictures of trees and flowers and fairies.

     Ma said that Jack Frost came in the night and made the pictures, while everyone was asleep. Laura thought that Jack Frost was a little man all snowy white, wearing a glittering white pointed cap and soft white knee-boots made of deer-skin.  His coat was white and his mittens were white, and he did not carry a gun on his back, but in his hands he had shining sharp tools with which he carved the pictures.

~ from Little House in the Big Woods,

written by Laura Ingalls Wilder

One of the things I remember clearly from my own childhood is searching for new pictures from Jack Frost every winter morning.  We lived in an older house, and many of our windows would be covered in frost around the edges on cold, cold mornings.  The image of Jack Frost in my head was similar to that of Laura's above.  I was always impressed by his beautiful artistry!