I love doing snow storytimes in winter. Alice Schertle begins ALL YOU NEED FOR A SNOWMAN when the first snowflake falls. SNOWBALLS by Lois Ehlert also deals with building a snowman.
An older song that I remember (and can be found on the internet) is Suzy Snowflake. She comes tapping on the window and offers to help build a snowman and take them on a sleigh ride. I'm planning on making a flannelboard to go with the song.
Another song that has picture book editions is FROSTY THE SNOWMAN. This is always a favorite & although we hear it during the Christmas season, the song itself never mentions the holiday. This means it can be used throughout the winter.
A quick and easy flannelboard is "Counting Snowflakes". I used some snowflake calendar cutouts & put sandpaper (you can also use velcro or felt) on the back. You can count up as you put them on the board & down as you take them off.