Have some neighbors who are taking a cruise to Quebec the 2nd weekend in September. What can they expect for temps? I would only head up in late November through March for hockey tournaments so I'm not certain what September would be like.
We are having a nice August now, and Sept. looks good. Today was 77*, tonight down to 58*, you can expect a little cooler than this in a few weeks, but not by much. Mid 60's during the day, mid 50's at night is average. Cooler on the water, Hoodies and sweatshirts are good to bring. Hope this helps. cheers