Well, if you don't like too much wind
you are not necessarily at best spot, Turkish coasts are much quiter. Assuming that you will stay in greek waters for 4 weeks, to the south Nsiros, Simi, Tilos, Chalki and finally Rhodes are beatiful and you won't get too much wind. (not more than 20-25 kts) Anywhere west form this direction you risk to have stronger winds. Astipalia can be the last spot to the west. Mikanos, Santorini will not only have much more wind but also crowd..
It's quite unlikely to have a rainfall any time between June through mid september in this area.