I know the calendar still says Summer, but I think for most of us on the great Pacific Northwest Coast, we would see the Labour Day Weekend as the recognition of Fall.
The first part of September can be great, same sunny days as enjoyed in August, same great boating options in the Gulf Islands/San Juan Islands, but it does get darker earlier, and there can be fog slithering about in the mornings.
Lots of Farmers Markets, food and wine pairing events (on Salt Spring, it's the Sip & Savour weekend to enjoy), Fall Fairs...all to enjoy the Harvest in September.
Enjoy your weekend, take part in the fun events, and look forward to a super Fall season.