Sleeveless, knees showing, FitFlops.

Wear what you want to wear where you want to wear it.

Show respect in places of worship regardless of which religion it is. In Moslem places take off your shoes and cover your head. In Christian places cover both your knees and shoulders. In Bahá'í places take your shoes off.

It just shows respect.

We are currently in Normandy. We were at St Michel 2 days ago. Spent 9 days in Paris before that. It's all casual, I wear fit flops but do not recommend them for climbing all the stone steps. You do see some shorts in young girls but more likely summer dresses. Easy to add a scarf if necessary. It's warm here now but not hot like Paris! We were in Paris and I was with a group of students. Even at Notre Dame no one cares about the shoulders or knee thing! It's a bigger deal in Spain and Italy.
Have a fun trip
Linda

Linda - you have a very unfortunate typo in your message. Please correct or remove it.

For the OP, where do you get the idea that you can't wear shorts and tank tops? Of course you can!

I already PMd Linda about the typo. Hope she wakes up soon to correct it!

two typos actually

What's the second typo?

shorts in young girls

maybe shorts on young girls?

This is why people should take just a few seconds and reread their posts. Most don't.

And auto corrections can pop up on words that are used previously, so this is rather potentially embarassing.

I agree. FitFlops are amazing. Even my podiatrist likes them. I'm taking a pair on our trip this summer for when my toes hate my shoes.

Flip flops (and just changing the name doesn't make them not flip flops) are a bad idea on uneven streets and sidewalks. You need shoes that will stay on your feet. It's the same safety issue LOL!

Tanks and Shorts are fine in France. I was just in Paris and with the heat, I saw lots of people in shorts. I will say take into consideration modesty and fashion. A Short and Tank can look very chic if done properly. If you plan on going in a church just take a light scarf you can tie around your waist sarong style (I saw lots of people doing this).

People that are not familiar with a good pair of Flip Flops would not know the difference or the benefits. A good pair can provide body alignment with a deep heel, arch support, and comfort. FitFlops have such high reviews on Zappos and Amazon and appear to be amazing both for your feet, back and legs. My Flip Flops (Orthaheel) are orthopedic and I travel in them all the time and they are great! My travel Sandals is from Aetrix and they have great support and a slight heel, I walked all day in them! So take what you know is comfortable, traveling is not the time to try a new shoe.

There are some churches still that publicly post a dress code and will turn you away but not in the area OP intends to travel. (for future consideration - Barcelona). The Catholic church actually does have a global dress code, but it is up to the church's pastor, bishop, whomever - whether to enforce or not. I expect there aren't enough people they can avail from in order to enforce and the money from tourism is too great to turn people away.
well chosen loose fitting natural fabrics or performance fabrics can be cooler than a lot of skin exposed to sun and sunburn.
I also question the stability of a flipflop on cobblestone or with 6-8 inch curbs and uneven pavements. European landscape is just a lot different and harder on body and shoes than North American pavement. I fondly (not!!!) recall having to pick up my mother from the airport having been transported by air from Amsterdam cutting her vacation short for inadequate footwear and high curbs. Broken bones, huge swollen foot, and close call with thrombosis. On the other hand, Netherlands is where you want to do it - free health care and even free crutches....
I wear sandals. both no heel, one with suede thin straps by Keen, and another high priced walking sandal to take my orthotics - they have a full enclosed heel and a lot of side support. Worn everywhere from Paris to Machu Picchu with that pair.

The shoulders and knees covered advice is for visiting churches. The rest of the time sleeveless tops are fine and very common. Shorts, too. Shorts aren't fashionable so people looking to blend in prefer to avoid them -but they are allowed and not offensive or anything. Just out-of-style. Capris (men and women) or skirts and dresses (any length) aremore popular. But wear what you like. Just have something to cover up in churches that require it. A scarf or cardigan or raincoat.

I don't know fitflops. If they are comfortable on uneven ground for miles upon miles of walking then I see no problem.

I had to look up FitFlops to see what they were. I see that they have loafers and and sneakers and strap sandals but I think you are probably asking about their toe thong sandals. I have never worn them and cannot speak from experience but I do not think they are a good idea. I just don't think they are going to work on the cobblestone streets. I saw a woman trip and fall like heavy stone on the cobblestones outside the entrance to Versailles. She was wearing wedge heel flip flops. She literally was not moving when someone finally ran off to call an ambulance. It's a dramatic example and something I had never seen before but I have also never seen someone pitch forward and fall that hard. I actually wondered if she had a stroke or something like that and the fall resulted from it.
No one will say anything to you about what you wear in Paris and I have never seen anyone stopped based on attire at any of the churches that I have been to France, which is quite unlike my experiences in Italy. I have also seen loads of people wearing shorts all over France -- some were no doubt tourists but I know for a fact that some are French. The thing that I notice in France about women in shorts is that they are not as prevalent on women over around age 25 as they are in the United States. I don't wear shorts except to the beach and in parks or country settings but I know many people who do wear shorts in Paris (they live there year round) and they have not had any problems or issues. Shorts are not unfashionable. You just have to wear the right ones to the right places. The people I know in Paris wear shorts when it is extremely hot and they are going to the park or just sort of strolling around and not when they are going out to dinner. As with most things, it's a judgment call based on where you are going. In Normandy, shorts should be fine if it is hot just as they are on the Cote d'Azur and same for Paris but recognize that there are some restaurants and other places where they will not be appropriate attire.

As to your specific questions in order: Skorts are okay but generally in my view they look silly on anyone over 10. Yes to capris or a skirt mainly because you will not be worried about the shorts issue. There is generally no rule about covering shoulders and knees. Sleeveless and collarless shirt is fine. Yes to sundresses. No need to cover your shoulders. As to the knee vs the shoulder, there is no rule.

It's very refreshing how you can never go wrong with a knee-length skirt. And they're the coolest thing you could possibly wear. I'm going to be stuck bringing a pair of stretch trousers on my late July trip because I need them on the plane or I'll freeze. The rest of the time I'll be wearing skirts and dresses. Nothing fancy, just simple things, but I know I'll always look tidy and sophisticated.

I am travelling to Nice in early September and will probably bring a skort, at least one Capri and lighter cropped leggings. One pair of long pants for plane. I am now on the lookout for thin cotton sun dresses that I wear bike shorts with for the thigh rub issue! I have dresses but they are thicker polyester like materials. I saw some rayon today but am unsure if they would be cool enough. I wear skirts and capris at home but want to be as cool as possible when using public transit and being on foot.

A friend visited Croatia last July and wore cotton sundresses as did most Europeans.

Wear your tank tops and bring a scarf in your day bag or purse large enough to cover shoulders for churches. Wear shorts if you like being aware some sights may not allow you in. In Milan, years ago, I did see one guard turn away a girl in a tank top; she did get it and put her thin sweater on. I cannot remember what she wore for bottoms. She was allowed in after donning the sweater.

I have a pair of FitFlop brand lace up canvas shoes. So comfy. Sort of like a boat shoe, in black with white sole. They will be in the carry on to Europe this fall.

Skirts and dresses = horrible chafing for those of us with some meat on our bones. I have to wear spanx then to avoid the chafing and spanx are horribly hot.

I think I have to try those Fitflops...maybe toe thongs for home, and one of the sandals may work for travel. Needing orthotics or a sturdy base makes shoe buying challenging, but these footbed choices may work.

I wore sneakers/trainers in Munich last year. Within a few hours, I had serious pains up my shins.
I felt as if I felt every cobblestone with every step.

I went back to my hotel, switched to my FitFlops and never looked back. I could walk on anything, the pain in my shins went away the next day.
I'm flat footed and have knock knees and have never been able to wear flip-flops in my life. There's no support. But FitFlops? It's a whole different story.

I'm hoping that they wouldn't be compared to flip-flops for my trip to Italy this year. Bring on those cobblestones!

I've never worn FitFlops (my disclaimer) but looking at them online they seem to generally have the side attachment point at the heel end rather than closer to the ball of the foot. My Merrell slides are similarly made and it makes a huge difference in how secure they are on your feet. I wore those Merrells all over Spain and central Europe with great comfort and stability. If the FitFlops you have are that way, I wouldn't worry a bit about comfort or safety on cobblestones.

Have a great trip!