WARNING SIGN

On the way home – after Wilson 'saw a ghost' – we came across this road sign, which for some reason he found hilarious.
He dragged me across to take a look, and I asked him what he found so funny?
'It's a sign warning drivers about a man putting up an umbrella', he giggled, 'and it's not even raining!'
I thought about putting him straight and explaining the meaning of the slightly ambiguous graphic, but then I thought better of it.
It does look a little like a man with an umbrella, and it's given Wilson a bit of a laugh, so really where's the harm…