Looking to book a trip through Priceline? Do it now, and you can be eligible for their Sunshine Guaranteed offer . Here are the details on this “rain or shine” promotion:

What’s it good for? By booking your summer vacation package (for departure between July 1st, 2008 and September 7th, 2008) now, you can get in on this deal! Get your trip to over 100 vacation destinations finalized before July 17th, and be sure that it is between 3-8 days long (travel dates included.) You must also be sure to book at least 12 days in advance.

What’s the Guarantee? If it rains more than ½ inch total accumulation on each of at least half the days of your vacation, your trip is free! So if you are vacationing for 3 days, you must have rainfall on 2 days. If you are traveling for 8 days, it must rain on 4. (Get it?) Your cost of airfare, hotel stay, rental car, attractions booked through Priceline, and all taxes and fees are included in the refund.

Who keeps track of the weather? Priceline, of course. And while you can use your own rain gauge or a trusty meteorologist to keep score, Priceline will keep tabs on the rainfall (provided by the National Weather Service) for your destination. Rainfall will be updated periodically via a special link, and if the moisture measures up, your refund will be automatically sent to you.

Is Seattle included? Were you going anyway? I wouldn’t make a special trip in hopes of getting something for free (it’s been a wacky year, after all.) But if you’re headed somewhere special and can’t decide on an online booking provider, this may be the way to go. Getting rained out is no fun, but even a week stuck in a hotel can be relaxing if it’s free!

For a complete list of destinations (which include Seattle, Key West, Toronto, and Philadelphia – plus too many to mention), visit Priceline’s guarantee page. (And try not to be too disturbed by Shatner's karate chop.)