Having learned to fly on the west coast, half the my instructional (dual) and solo flights were conducted in rain. I initially thought the question was a troll, as no licensed pilot would ask such a question. However...
I was cautioned in basic ground school and again on my Mountain Flying Checkout of the following optical illusion: "Rain on the windscreen can create an illusion of being at a higher altitude due to the horizon appearing lower than it is. This can result in the pilot flying a lower approach. Additionally, when flying in moderate and heavy rain, the crests of hills and mountain tops may appear lower than they actually are. Combined with a lee/mountain ridge downdraft, the flight may result in CFT."
Last edited by evansb; 7th Nov 2018 at 19:32.