You can create a snowpeople with the snowballs.
There should be a few snowballs lying around, roll them around snowy parts and they'll grow bigger, on pavement/sand to make they get smaller. You can roll one on top of the other and they'll turn into a snowperson, depending on the proportions of the balls rolled, you can create snowman, snowmam, snowboy or snowtyke, these give out different rewards when built correctly. Note that the snowball currently being rolled when you roll one into the the other will be the top one, so make sure you roll the smaller one into the bigger. Here's a list of the available snowpeople, conditions for getting them and their rewards, taken from here:
- Snowman: The Snowman is made by stacking two large-sized snowballs together. If he is made perfectly, he will ask the player to play bingo with him and give the player a bingo card which can not be dropped or deleted until January. This bingo card will have 24 random numbers on it, with a 'free spot' in the middle. Everyday until he melts, the player can return to him and play bingo. His eyes will spin, each displaying a number. If the number he displays matches any number on the player's bingo card, he will allow them to punch out that number. This number resets everyday when the player speaks to him. In addition, they can travel to other towns to speak to Snowman to get additional numbers that day. When the player gets bingo (5 numbers in a row) he will reward the player with a piece of the Ski Series.
- Snowmam: The Snowmam is made by stacking a small-sized snowball onto a medium-sized snowball. The third, smaller snowball on her head will appear automatically when the two are pushed together. Snowmam will ask the player to give her snowflakes which can be seen occasionally flying around during the winter months in the players town and can be caught with the net. If she is made perfectly, she will only ask for 3 snowflakes, however if she is made imperfectly, she will ask for 5. In exchange, she will reward the player with a piece of the Ice Series. The player can give her as many snowflakes a day as he or she likes.
- Snowboy: To make Snowboy, the player must roll two medium-sized snowballs - with the top just slightly smaller - together. If he is made perfectly, he will compliment the player and the player will receive a piece of the Snowman Series in the mail the next day. If he is made imperfectly, the player will receive nothing.
- Snowtyke: The Snowtyke is made by stacking two very small snowballs together. The Snowtyke will only give the player a gift when they have made the other three Snow People near him. He will reward the player with one of four items.