H&K Mum: You may want to pick up a used Interval International Resort Directory on eBay or through friends. (Perhaps someone at work has one?) Look for a book 2007 or older as the website and most recent directory (?) no longer show the traditional "Red, Yellow, Green" (high, medium, low) season charts.
EDITED!! I'm looking at my II [2007-200] Resort Directory now -- the seasons are displayed in the "Alphabetical index to resorts" near the back of the directory.