This is only how a cold weather person thinks about heat. That’s not how real life works.
One light layer of linen is amazing. Your body does the work on its own. Touregs in the Sahara wear a light layer of light fabric. Look at Saudis and the traditional outfit. Italy in the summer. All similar. All perfectly comfortable.


Every time I’ve been to Italy in the summer, north or south, everyone is in summer uniform. Same in Greece, but obviously the Italian version was fancier.
Unless… Are you an 80 year old man wearing polyester and wool and a vest and a hat in August on the farm?
Seriously, though, any search online for summer Italian wear is usual light clothing.