When I visited Rome, Italy, I ended up visiting during August which seems to be a time when most Italians have fled the city to cooler areas. This was nice because there was less traffic so we were able to move around better. At the same time, it was really quite hot, which was not as fun. I'm definitely not a fan of crowds, but I would rather deal with crowds than with bad weather and less activities.
What are the ideal times of the year to visit France, particularly Paris, balancing out weather, crowds (locals and tourists), and available activities (festivals and such)?