Can a person die from over exposure to rain?
Rain per se? No. But when you are wet, your body looses heat more quickly. If it's near freezing, windy, and raining you are in much more danger of developing hypothermia, or low body temperature. If your body temperature falls low enough, you can die. You may hear references to death from exposure, which is shorthand for "exposure to the elements", but the actual problem is hypothermia. If your feet are continuously wet for days and day, you may develop immersion foot, also called trench foot:


  Trench foot is a medical condition caused by prolonged exposure of the
  feet to damp, unsanitary, and cold conditions. The use of the word
  trench in the name of this condition is a reference to trench warfare,
  mainly associated with World War I. Affected feet may become numb,
  affected by erythrosis (turning red) or cyanosis (turning blue) as a
  result of poor vascular supply, and feet may begin to have a decaying
  odour due to the possibility of the early stages of necrosis setting
  in. As the condition worsens, feet may also begin to swell. Advanced
  trench foot often involves blisters and open sores, which lead to
  fungal infections; this is sometimes called tropical ulcer (jungle
  rot).