Hi Carly,
We're going then and we asked anyone and everyone when we were there in June this year and the Turks told us it was warm in the day time but chilly/cold at night and told us we'd need a jacket/coat.
The expats we spoke to told us it's still warm but you'd need a cardigan or light jacket at night and there is possibilities of showers but apparently they only last a short time but when it comes down it lashes down.
I'd go with the expats opinion as some Turks were wearing jumpers in June