It depends to some extent on what you’re looking for. Late May, June and early July is considered the best time for seeing orca whales. The islands are less crowded then, but offer greater probabilities of getting variable weather. July and August generally offer the best weather in terms of less precipitation. The downside is that there is usually more boat traffic. My personal favorite is the month of September. Paddling after Labor Day offers fewer people, the weather is usually still good and you generally have your pick of campsites.