Being out in the rain makes you more susceptible to getting an infection. It lowers your body temperature which in turn slows down your antibodies and white blood cells. The reason you get a fever is because it increases the productivity of your immune system. By slowing it down, it cannot do the job it normally does. So the bacteria that your body normally fights off, isn't getting fought as much. Your body is covered by all sorts of bacteria as well as having tons of bacteria in your mouth, lungs,