There is really no reason to have air conditioning in Vancouver, but the place we bought came with it and so now we have become wimps and are totally reliant on it - and Booker as well! When it gets even the least bit warm she slows down to almost a crawl on our walks in the horrible un-airconditioned outside world (unless we are going towards a pet store where she has the prospect of a treat, then she runs...). The other two don't seem to be much different whatever the temperature, though.