Hi Pondskater....
We did the 10th to the 24th a couple of years back in 2004.
Just missed a big storm two days earlier and the sea was well up on all the beaches on the first couple of days as the storm surge was still in the Mediterranean.
Found it much cooler in the evenings than in early June when i had previously visited the island for a holiday. Sitting around the restaurants, tavernas and bars was OK but, i anticipated the walks back to our apartments and i had light summer jackets as i don't drink enough to get a free beer coat...
I think you have to make a personal choice on whether you take a cardi / jacket or not and base your choice on would it spoil your evenings out if you felt a chill and needed one.
You can check the weather history going back a few years at Wunderground
28/05/2007
That's a link to the daily weather and if you "click" the weekly tab you see an average and also at the bottom of the page the daily reports.
Paul....