Meh, usually it really isn't that big of a deal. Getting rained on isn't the end of the world and it is usually best to just tough it out in my experience, but if you have the flexibility of using the leave at a later date and want to put it off, then just go later. If you can't postpone without losing your leave and really want to stay dry, hop on a train, plane, or bus and head for a drier locale.
Best to just take this stuff in stride. I have had to tough out bad conditions or change, postpone, or bail on touring, kayaking, backpacking, skiing, and other trips over the years for a variety of reasons including injuries, forest fires, altitude sickness, blizzards, floods, vehicle breakdowns, and family issues. I've been stuck holed up and snowed in during a planned trip unable to do the planned activity. It is all just part of the adventure of outdoor adventure activities.