Tug of Snow
Create a line in the snow using a stick and get yourself a large thick rope. This tug of war game will have your students slipping and sliding to try to pull the other team over the center line. Place 5 people from each team on either side (or more of the rope is bigger). One way to up the stakes is to make the snow in the middle extremely slushy by pouring a bucket of water. Another fun idea is to get a spray bottle with yellow food coloring to make the middle look like yellow snow.
Rolling It Up
Split your class into groups of three. The objective of each group is to roll the largest snowball they possibly can. The contest is over when the groups can no longer roll their snowballs. After you've judged the contest, let students have the freedom to combine their large snowballs to make snow men or any other snow creations they wish.
Snow Sculpture
Use this snow day opportunity to bring in a little bit of academic work. Divide your class into groups of 3 to 5 people each and have them choose a character from a story that you have read in class. Make sure that none of the groups pick the same character. Have the groups create a snow sculpture based on that character. After they have created the sculpture have them talk about the character and how it likes being a snowman.
Curling
Though you may not have a large sheet of ice and the equipment for Olympic curling, this event will help you to come close. You will need jumping ropes, bean bags and 2 hula hoops. Divide your class into two different teams. Each team will try to throw a bean bag into a "house" scoring area which is comprised of a jumping rope made into a circle on the ground about twice the size of a hula hoop within the rope. Students receive 1 point for getting the bean bag within the rope, 2 points for getting it in the hoop, and 3 points at your discretion for getting the ball in the center of the hoop. Though this may not happen very often in the snow, students can knock other bean bags out of the house area to stop the other teams from getting points.
Target Practice
Students will want to throw snowballs. Help them get it out of their system by setting up targets of popular movie villains. Print out some targets and have the students throw the snowballs at them instead of at each other. You can divide the class into groups if you wish and create a scoring system.