Weather can be very unpredictable in the Bay of Biscay.I have personally experienced storm force winds there in June. Have also crossed in December and it was like a millpond.
Type your answer here...We did a canaries cruise on board the Oceana 17-30th September 2006 and the sea conditions were great. We have been to the canaries many times before on holiday and loved calling there again on the cruise but our favourite place was definitely Madeira, don't miss going on one of the trips.
Travelled from Southampton middle of October couple of years ago. On a large ship - Sea Princess and the weather was a bit rough. Through the Bay of Biscay they provided sick bags and there was a lot of ill passengers, my personal experience is that I would not advise a Southampton trip this time of year. Been in May/June and it's been fine.