Christmas/winter party?

Not necessarily--any party can be pulled off with just the right touches. Depends what it is...care to elaborate what you have in mind?

Edit: There has always been a "Christmas in July" thing, so your idea isn't unusual--just don't make people wear snowsuits ;). You can make it a cozy cabin feel-use small tree branches (like from birch) to hollow out for tea light candles. Wrap candies or small prizes in ornament balls from craft store...tie ribbon at the top, can be take-home favors. Use a sparkle netting as an overlay on a red tablecloth to display the foods. Appetizers on mirrors to look like ice. Play a gift exchange where everyone brings a gift then each picks a number. First person takes a gift (can open it or not). Second person chooses to take gift from someone or get a new one and so on until everyone is done.

sounds cool, be sure to turn the air conditioning to 65 and turn on or light logs in the fireplace, play Christmas cd's, have pumpkin pie, hot apple cider, turkey sandwiches! wish i could come over... have everyone bring a 5.00 wrapped gift , with no name on it, and play secret santa...

Your birthday, your prerogative. Don't let anyone else tell you different. It's your day.

Do what you want. Remember, FREEDOM IN AMERICA !