In 2009, he was diagnosed with progressive supranuclear palsy, with a few years to live. Rainwater spent over $20 million on research trying to fight the disease. In 2010, he was awarded the Arbuckle Award at Stanford University. In accepting the award, he began to cry, showing the effect of his disease on his emotions. That year, he made his last public appearance. In March 2011, a court declared him incapacitated, and his youngest child, Matthew, became his legal guardian. Rainwater died on September 27, 2015.