Temperatures are relatively mild throughout the year in Ile-de-France. In the winter, average temperatures range in the upper 30s to low 40s, although its possible that in the depths of winter it can get very chiily and there can be rain as well. During the summer, temperatures average in the upper 60s to low 70s, although conditions can be quite hot and uncomfortable in late July and August.

If you want to avoid the crowds, it is best not to travel to Ile-de-France in the summertime, when everyone and their backpacking mother tromps through Europe. Instead, plan to travel in late spring (May, June) or early fall (September, October), when not only are the crowds thinner, but the weather is a bit more pleasant as well.

Do note that museums tend to be closed at least one day a week, often this occurs on a Monday or Tuesday. Check museum schedules before you go; also note that many museums, such as the Louvre, offer extended hours one or two nights a week as well.