shallow query for MNers in Paris

[AuldAlliance]

I am off to a conference in Paris (Fri, Sat, Sun) and am diverting my attention away from the fact that my paper isn't ready yet by wondering about what to wear. May is a tricky time of year, when it's hot down where I am but could be chilly in Paris. Or coolish but sticky in the metro.
Can you advise?

Short sleeves or 3/4 length?
Bare feet and sandals or closed shoes?
Blazer or linen jacket?

TIA for any help...

AA, the weather is forecast to be fairly warm this weekend with highs of 25/26° I think.

I will let the Parisian ladies advise on what to wear though... I am going to Paris on Sunday and planning on wearing a linen dress with no jacket (I will be outdoors all day).

Oh, it will be warm this weekend, they're saying even up to 30 degrees. Definitely sandals, dress or short sleeves and then have a cardigan/linen jacket just in case. It's about 21 degrees here now and I'm in a T-shirt-I think it must depend on the humidity etc. Sun is really strong.

Thanks for your quick replies...!
Must finish the damn paper, then I will fret in more detail about what to wear.