Haze and humidity at Loweswater

We climbed Low Fell above Loweswater. Although the sky was cloudless, the visibility was poor. We could just about make out Great Gable about 10 miles away. That whiteness is characteristic of Mie Scattering from water vapour that I have posted about before. I was wondering whether it was to do with this current warm air from the Caribbean. Is it that it holds more water vapour than cold air and so is the humidity actually high today, even though it is warm and dry? I checked and the reading for humidity at Keswick was 71%. But then I found this: https://en.wikipedia.org/wiki/Visibility The visibility in the picture can't be called HAZE because you can see further than 3 miles. The earlier part of the article discusses the derivation of a rigorous formula to calculate the distance that should be able to be seen. That will take some thinking about.