Weather in May/June is better for us. Some days around 80 degress, some days higher! Also had a couple of cloudy days and some rain. Cooler at night which makes it more pleasant.
Dalyan is such a great place. Nice bars to chill out in and not full of people like the larger resorts. Also only 20 minutes from Dalaman
airport so no massive journey to your resort once you land. We stayed in Villa Samimi and got a really good deal for just two of us using the villa which would normally sleep 6. We've stayed there 3 times now and it feels like our own home. Did a jeep safara and the 12 Island Tour from Gocek and basically relaxed the rest of the time.