Clothings/temperature in Paris/Rome by mid-May
 

I wonder if it is necessary to wear a sweater in the day or night during mid-May ?
Is one collared t-shirt alone for a strong male enough ?
I can check the temperature online but being one from a hot Asian country and lacking travel experience, I cannot figure it out.

Best bet is to check a ten or fifteen day forecast online just ahead of departure to finalize your packing. Pay attention the the lows as well as the highs, and know that this time of year those highs, if reached, will be only for a few hours at best mid-day.

It will likely be chilly mornings and evenings. If you're used to hot weather, you probably most definitely will need outerwear...recommend something windproof/waterproof and something warmer for underneath. For sure, you'll need one or the other or both throughout your visit.

We frequently visit Paris in May, and I usually find a shirt and jacket -- blazer -- sufficient unless it is raining. I sometimes wear a dark T shirt or polo shirt (knit but with collar) under a black or blue blazer, though this may be cool in the evening.

If you are opposed to wearing a blazer or other sports jacket, as many who post here are, you will definitely need a windbreaker/rain jacket of some sort. But I don't think you are likely to need a sweater.

It depends and can be variable....so bring one jumper/jacket at least

>>>Best bet is to check a ten or fifteen day forecast <<<

Forget this. Paris has Atlantic climate - no forecast which exceeds three days is reliable.

Temps will be between 15°C - which is pretty chilly - and 30°C - which is pretty warm. Be prepared for rainy days. I would pack short-sleeved shirts and a light jacket, but no sweater.

Elegance of clothing depends on the restaurants you want to visit. Unless you want to go a very posh place, smart casual clothing will be sufficient. In Europe, the overall impression (matching colours, smart shoes) matters, not the single item. If you are dressing in the style of your home country, it will be greatly appreciated by Europeans.

Last May it was pretty chilly and rainy,bring layers,

Thank you very much.

Defying all meteorological logic, (non-working) Parisians and tourists alike are wearing shorts and flip flops today. It has been 26° for the last two days and feels even warmer because nobody is used to it.

(Some) 20ish women are wearing hot pants. Now that it a 'fashion' that I hoped never to see again.

"If you are dressing in the style of your home country, it will be greatly appreciated by Europeans"? Isn't that an interesting comment - bring out the white tennis shoes!

Bring the sweater.

If you need it, you have it.

If you do not bring it and you need it, you don't have it.

Or you can buy one after you arrive and have a long lasting souvenir.

Something waterproof wouldn't hurt. When I was in Paris 2 years ago in May it went from warm to pouring rain within a four day period.

>>>"If you are dressing in the style of your home country, it will be greatly appreciated by Europeans"? Isn't that an interesting comment - bring out the white tennis shoes!<<<

Don't overdo it! Kimono, greatly appreciated. Buddhist robe - greatly appreciated. Caftan - greatly appreciated. But white tennis shoes - no-go. You stretch it too far.

All this talk of weather- be sure to pack a light-weight travel umbrella!