Hi,
The first time I went to Plakias was way back in 1990 on a rambling holiday, but it was the last week in April and the first week in May. From what I can remember of the weather it was mixed, i.e. some days it was hot and sunny - sunbathing weather without being overpowering - and other days it was overcast (or partially) and good walking weather, but a sweater was needed at times. I don't remember any rain or the high winds that I've come to expect when I've been since in the summer. In the evenings we usually ate inside. The good things are that you will see all the spring flowers and if you venture down the Samaria gorge, there'll be water in the stream.
Greecemad.