Hmm, I like this. It's a really quick way to check likely weather conditions pretty much anywhere around the world (1400 locations). It's compiled by some people at Pinewood Studios who tell film producers where to go to get the weather they want.
But I wouldn't rely on it too much.
It may tell you what the weather 'should' be like for your forthcoming holiday, but it is not a forecast - just an historical average.
In all my years of travelling THE most common greeting on arrival at any destination has been: "Oh no, this weather is MOST unusual for this time of year! Pity you didn't come last week!!"
... You know. That's what they say when you arrive in Istanbul airport in March and look forlornly at the thin layer of snow on the ground.
I mean, just ask anybody from the seaside towns of America's Gulf Coast if they feel they've had normal weather this summer!