Illusion of Not Raining

Illusions coinspire me to write about magic. Because I wonder how on one side of the house it seems to be raining but on the other side of the house it seems perfectly dry. Bizarre isn't it? Before I said, "aww, poor wet dog" to my dog, Dancer, I noticed that seemingly dry side was brighter than the raining side. Is this a coincidence or is it part of the illusion, somehow?