Early May can be iffy, your best chance has to be well south maybe Crete or Rhodes, even Cyprus is not certain at this time of year.

I was going to say the same. May in Crete is hot enough to sunbathe without being too hot, certainly early or late season I would head south to Crete or Rhodes.

Symi and Kos would be fine too.

May and September are my favorites months to holiday in Greece although been to many Islands Kefalonia is our favorite and have stayed there every month from May to October the weather differs so much, from year to year, we had it roasting in May, wet, really nice, to cold, I agree Rhodes or Crete could be more stable.
pojo

We went to Kephalonia in early May and the weather was lovely, got a nice tan, not too hot. However, pools and sea were freezing.

sarah

Been to Rhodes in early May and the weeather was glorious

We went to Zante at end of 26th April 2003 and it was 30deg plus!

We stayed just outside Laganas in a village on the beach, Aghios Sostis. We could walk into Laganas if we wanted and that had some nightlife
For us with 2 kids it was fine until about 11pm.

Hi

As Nicola above states zante can be lovely as early as April.

I went to Laganas 2004 10th - 24th May and it was fantastic weather with only one slightly overcast day in 14. Visiting other parts of the island i noticed that the Laganas bay area got more hours of sunshine and was virtually windless compared to other resorts. i swam in the sea most days and spent a couple of days scuba diving and found that i would swim in and out of warmer areas, it wasn't a problem.

It's not just the time of year you need to choose the resort carefully to get the best weather early in the year for any island.

Hi,i have been to cyprus in both april and may and the weather was super both occasions-late 20's and i was able to swim in both the sea and hotel pool,we stayed in limassol and ayia napa and both were fairly lively without being mad which was fine,cheers Mark

Been to Kos end of may kardamena and it was very hot but with a very welcoming breeze just don't be fooled by the breeze thats how you get burnt. Going next year 24th May to tingaki and hoping for the same.
Sam x