Never! With a heading of due south and no one touching the helm
you'd run aground in the Haida Gwaii (and they really don't like boats littering the shoreline there).
But, if you set the course to just clear the Haida Gwaii (somewhere around 170, but don't have the plotter up), and used an auto-pilot tied to the GPS
to eliminate cross-track error, then it could be done pretty much all summer and into the fall. Winter and spring you run a much greater chance of running into a southerly. Have a look at the pilot charts
, you'll see it pretty clearly.