My wife and I are planning our next vacation. My wife is adverse to "cold and wet". I visited Scotland several times when I was in the US Navy, I recall a few nice days but lots of "cold and wet". I have been to Glasgow, Edinburgh, and a small town called Dunoon. For the best chance of [some] sunny weather what would be the best month/week for us to visit?

We would like to see the ruins of Dunbar castle, perhaps Edinburgh, and some out of the way towns/villages in the highlands.

Thanks for your responses.
Rondo