Air Conditioning in Arcachon Bay in late July?

I hope someone can answer your question but you should know that most apartments, rental cottages, and homes in Europe do not offer A/C.

Based on Wunderground.com's day-by-day historical data, I would want air conditioning unless I was booking just a day or two ahead of time and could see a reliable weather forecast and knew the temperatures were going to be moderate. I've linked to the actual data for July 2017. You can look also at 2016, 2015, etc., to get a more complete picture of what you might experience.

One option would be to try to find a hotel that has air conditioning. The French term for that is climatisation.

Find a hotel that has air-conditioning. Rental apartments do not have it.

A definite maybe. It should be more comfortable on the coast but very hot days can happen.

Thanks so much! We booked a hotel with A/C.