Weather in May

I've been to Italy in May a few times. Here was my experience:

May 1997 - 3 weeks in Tuscany. Idyllic weather, bordering on hot. We went to the beach.

May 2019 - started in Northern Italy. Around Lake Como it was mostly sunny with a few storms blowing through. Not super warm, but we ate outside often. Verona -- it was rainy. Lake Garda -- sunny but not very warm. Dolomites -- very grey, not warm. At this point I was reading in the news that it was the coldest May in Italy in 50 years. By the time we got to the Cinque Terre and Tuscany, the weather was idyllic. Not hot, but warm and sunny

May 2023 - early May in Tuscany. Mostly sunny and warm. We went to the beach. There was some rain, but nothing that ruined our plans.

Anecdotal, but I hope that helps

Simple: May is as good as it gets. The iris are blooming in May and they know best.

I usually travel in late May (going on 20 years now), but it has been near perfection in all years but one. Last year was awful, with flooding rain.
All bets are off--climate is out of wack--so just keep watching the ten day forecast. But cool nights are absolutely guaranteed, and I always take a good raincoat, spring or fall.

May 2001 - Venice, Florence, Siena and Tuscany, Rome, Amalfi Coast - pleasant temps, one day of heavy rain in Florence otherwise sunny. April/May 2022 - Sicily, Rome and parts south - pleasant temps, a brief drizzle in Siracusa, otherwise sunny. A plus to visiting in May are the wildflowers in bloom. I especially will always remember the fields of poppies in Tuscany. It will not be warm enough to go swimming imho. Bring a raincoat just in case.

Last year we were in Northern Italy (Milan and Lakes Orta and Maggiore) the first 2 weeks of May. It was VERY wet -- so much so that one of our hiking days ended up being a taxi day because it poured. We used our rain jackets more than I had thought we would and it's true -- the visions I had of aperotivo along the waterfront didn't happen because it was mostly too wet. (This was when Emilio-Regellia had terrible flooding and they had to cancel the F-1 race, etc).

That said, sometimes weather is all relative. We were coming from such a cold, wet spring here in the PacNW (abnormally cold) that even though it was wet it was 20 deg warmer where we were in Italy. And we had several simply perfect days of high 60s and sun. So for us the rain wasn't terrible -- it wasn't exactly what we had hoped for but it certainly didn't ruin anything. And for us it was so much warmer and we were so tired of being cold that it was better regardless :)

Ravello is so pretty! I hope you have wonderful, clear skies there!

I’ve been watching for the same time period. I will be in the Puglia, Sicily, Abruzzo, Lazio & Umbria regions. One place in Puglia has a small pool, and I’m also staying in Polignano a Mare for a few days. Swimsuit for the pool/beach has been my question. Otherwise, I mostly have my few clothes decided.

I would consider early-mid May a major stretch for swimming--only a heated pool.
I have swam in late May, but it was very cold sea water--refreshing if it's a hot day and you've been active. The sea just takes time to warm up.