A number of ways to do it:
VRBO.com Vacation Rental By Owner
List with a REALTOR that specializes in seasonal rentals
Post it on your Facebook Page - you never know which one of your friends knows someone needing a place.
What ever you do make sure you get deposits, inventory your belongings, don't leave anything there you would be devastated about if broken or stolen, check with your insurance agent about what changes to your policy might be needed, run credit and background on your tenants and realize that you may not find someone for the entire 4 months, but if you can get most of it filled be grateful (just don't fill only February or a week later someone will want Jan-Mar).
WEST USA REALTY