As a first time tourist to the UK, back in the early 80's I made the obligatory trip to Trafalgar Square to feed the pigeons. I was commenting on the dreary grey weather and looked up at the sky. At that point a pigeon "thanked" me by painting my forehead with crap. As I stood there madly wiping it off my then future brother in law commented that it was a common feature of English weather to rain birdshit, he claimed it is where the term shitstorm originated.