Seeing the museums is high on the list, and figured that was pretty weather-unrelated. It's good to hear they're less crowded

There are still lines to get into the biggies, and long lines at the coat check.

Wear something that will go into the museum(for me sportcoat, sweater, cap & backpack). Then get a week long museum ticket (Carte Orange?). You can get them in most museums with the card.

When you get to the museum, walk around the lines, and ask a guard where to go in with one of these, and show him the card.

Even if you don't use the whole card, it's worth the time saved.