I want to take a tour of Notre Dame in July. I'm assuming that Sunday is the most crowded day and that first thing in the morning is the best time. True?

sorry, no answer to your Notre Dame question, but picked this thread as it is your shortest!
Felt I had to reach out, as the V in my name is short for Val What part of Canada are you from?

Notre Dame is open daily to the public from approximately 8am to 6.45pm (later at the weekends). On Saturdays it is closed around lunchtime for maintenance work. Guided tours in English are conducted on Wednesdays and Thursdays at noon, and on a daily basis in the summer months. Opening times are sometimes subject to change and I've known people turn up and find it closed but that is a rarity.

Hey, Val! I'm from Edmonton.

Thanks, Kaneda, for opening times but do you have any suggestions on when the lineups are shortest?

I would get there before it opens, and be the first in line if possible.
Otherwise the lines in July could get quite long.

If you are going to climb to the top, which I recommend to see the gargoyles and get a great view of Paris, I suggest you arrive at least a half hour before opening time. When the door opens, the line is already very long and only a few people are allowed up at a time.