By the time he died, Rainwater had donated more than $380 million to organizations working for the benefit of higher education, at-risk children, and research associated with neurodegeneration. He left nearly all of his estate for charitable purposes, primarily through the Rainwater Charitable Foundation. In 2019, the Rainwater Charitable awarded its two first prizes: one for outstanding innovation in neurodegenerative disease research to Dr. Michel Goedert (MRC, Cambridge, UK) and one for innovative early-career scientist to Dr. Patrick Hsu (Univ. California, Berkeley, USA). Rainwater also left $5 million to UT Austin for the study of American music. His will and testament also provided $60 million to his wife, Darla Moore.