To most people a rainy day is a downer, a disappointment.... no blue sky, no clear sunshine, etc. But to me a rainy day is a beautiful day. The rain kind of calms things down, people clear out, they run inside to avoid getting wet--and blessedly-- the streets and sidewalks clear out, leaving it to those few persons that actually enjoy walking in the rain.
Things look calmer, the rain makes little reflecting pools and mirrors of most surfaces, so that even the most plain and colorless landscape looks interesting. Have you noticed how in a lot of movies when they want to make the scene more dramatic and interesting they add rain? It's because rain adds an element of mystery -- an air of uncertainty, that makes you think.
I also, love the fact that a rainy day reminds people that no matter how much we think we control nature, we can't control it. We may rant about too much or too little rain, but we can't control it, and this drives some people to distraction! To me -- rain just shows us that we are but one small part of the larger scheme of nature.