Yesterday, driving between Farnham and Guildford along the Hogs back
(A31) about Noon, I stopped at a lay by and was easily able to see the
Wembley Arch 28 miles away with unaided vision. Further on near
Guildford I was able to see the "Gherkin" and the London Eye. Never
before have I seen these from that location but never before have I
searched for them.

My question is, was the visibility exceptional yesterday. Judging by
the distance I saw I would think so. To save driving to the same
location only to get a poor view, what weather parameters (and where
to find them) do I need to check for great visibility. I assume low
humidity and no precipitation are necessary but is that all?

Thanks for reading