We took the floatplane/cruise trip out of Ketchikan last May and the weather was superb...clear and beautiful. Also saw a bear on the cruise portion of that trip. We're doing the exact cruise again this year in May...can't wait! My understanding from locals is that May is one of the driest and sunniest months in southeastern Alaska. We found that to be true. My parents went up there in July and it rained nearly every day.