I used to live in both New York and Paris. I'm also from the West Coast (S.F.) and I've been to Boston several times in summer.
Good news; NO, it's much less humid.
The reality is that while it's less humid, it's not all air-conditioned like N.Y. and Boston are. I, personally, being from California, am used to heat, but not used to humidity. I also abhor air conditioning so since it's mostly lacking here, it doesn't bother me that much. You can get sticky and hot, but it wont be like it is on the East Coast. It's more comfortable and you can walk around, seeing the sights without passing out or feeling faint. You can get hazy days but far fewer than on the East Coast, which is more humid that the West Coast but that's super-dry so not a fair comparison.
Paris is not near the coast so you don't get the ocean breezes that make the cities on the Pacific so much more comfortable at higher temperatures. So it can get very still and stifling at 80•F.
You'll also notice what my Philadelphia-born mother calls "dirty fingernail syndrome" especially with so many other people around. You'll want to take a shower and after a long day of sightseeing, you'll feel a bit grubby but you wont have that wet hair you get on the East Coast in summer.
What is much better are the Métro stations. I used to DIE in the N.Y. subway stations in summer. The trains themselves were air conditioned but the stations were sweat-houses. The Métro stations can actually be cooler than outside. I only find them uncomfortable when there are a lot of people crammed in them, like at rush hour.
Speaking of, be warned; the French have a different idea about personal cleanliness. I get laughed at here for my daily showers and still use deodorant from the U.S. The stuff sold here just doesn't keep me as odor-free as I need! Let's just say, you don't want to get too close and when it gets warm, it gets smelly fast. Since it's not hot here that much of the year, this is usually not a big deal.
It also rains in the summer here in France, so you do want to bring a light raincoat just in case. One of those tiny ones that squish down into a small bag is good. Don't rely on an umbrella, which are awkward in crowds. Paris has that misty kind of rain, not the West Coast downpours, so you really want a jacket/coat with a hood.
What is weird here, which the lower latitude in the U.S. prevents are the long summer days. The sun sets after 10pm. This means that if it's a hot day, it's a very long, hot day. You'll be eating dinner with sunlight and heat. Back home solstice is 8:30 so by the time we went to bed, it was much more comfortable. I also have to keep an eye on the time since it doesn't look 7pm, when shops close. I easily forget stuff. You might find yourself asking yourself why you're hungry. It just doesn't *look* like dinner time lol!