I was just about to book my flight to Sardinia (Olbia airport - Costa Smeralda area) for the beginning of May (May 4 - 14) when I received a note from a friend telling me that it might be a bit chilly at that time. She also said stores and restaurants might not all be up and running by then. I chose May because I want to avoid the mass crowds of high season but I definitely want weather that is warm (not chilly!). At least 75 degrees (24 C). I also don't want to go when things are still closed down. Anyone have experience in early May? Is late May better? Or should I look into early June?

Any help is greatly appreciated! I literally was about to book my ticket today when I got her note!

Though I have not been to Sardinia, it is high on my list, and based on my research and several visits to Italy/environs, I would follow your friend's advice if you wish to swim. Even though it may still be relatively quiet, I think late May would be a much safer bet, and I have swam in the Mediterranean several times in late May (like last week of May). Finding a sheltered beach with a shallow sea bed will help as well, but I would definitely not hesitate to go in late May, good luck!

It’s a lovely area. I was there at the beginning of September 2018, and it wasn’t crowded, but everything was open. Sea water was warm, having benefited from warm sunshine all summer. From my experience in the Greek Islands water is cold in May, even at the end of the month, and Sardinia won’t be much different.
https://seatemperature.info/may/cost...mperature.html

Weather in May and October are comparable. Average about 73 degrees and generally not a lot of rain. We weren't there for the beaches, but later May or early June should provide a better shot for swimming. In 2018, we covered most of the island in mid-October. It was comfortable and very, very uncrowded. You will enjoy. Here is a link to our trip report: Sardinia! You Gotta Go!! 8 nights. October

We were in Sardinia in May, flew into Olbia and out of Alghero so were just in the north of the island. Weather was warm and sunny, we wore summer clothes but didn't swim. It wasn't super busy but also wasn't quiet. From memory, everything was open.

If you get the chance, the day trip by ferry to Bonifacio is wonderful. Take your passport.

I found early-mid June to be too cold for swimming in Corsica so I would expect the same for Sardinia. The air temps though were perfect.

Thank you! I will definitely look into Bonifacio! I appreciate the tip!

I'd look up historical weather to see what it's been in the past. Sites like accuweather and wunderground are very useful. Everyone has a different personal themostat. I once travelled with a friend who comes from a warmer climate than I: she thought it was cold while we were on holidays and I thought it was fine.

There is no fine weather gurarantee for May. The seawater will definitively be too cold for swimming whereas the air is rather warm (no hot!). There will be more than 15 sunny days throughout the month, but days with heavy rainfall cannot be excluded too.
Shoulder season: June, September and early October
High season: July
Top high season: first weekend of August until last weekend of August.
Until early July, seawater in Corsica is colder than in Sardinia. Porto Vecchio is warmer than the West Coast and the North Coast. The strait of Bonifacio is always windy.
Southern Sardinia (Villasimius etc.) is usually a bit warmer (air and seawater) and less windy than the North.