Having a winter birthday doesn't mean your party has to be inside. Angela's family took the celebration outdoors: My daughter's birthday is in December and while she longs to have a pool party or bouncy house like other kids do during milder weather for her 5th birthday we decided to embrace the time of year.
We met at a local park and had a snowflake hunt. We restyled an inexpensive piñata from a party store (using construction paper and a hot glue gun) to match felt bags bought in the dollar aisle at Target. We hid small clear bags of treats tied with sparkly snowflake and snowman gift tags all around the park and kids had a snowflake hunt just like your average Easter egg hunt in the spring. Each year our park district has a fantastic letters to Santa program during that time frame so we provided stationary for the kids to write letters to Santa (for which each received a customized letter back). We topped the day off with hot chocolate, snowflake cupcakes, and sled rides around the park courtesy of Dad.