Watch VoirFilms. The hottest summer on record left Austin ablaze and terrified, a city where heat hits hardest in at-risk neighborhoods and communities of color. In the aftermath, the Castañón family walks into the woods, asking: What is heat? At a city-run heat-mapping event, they trace invisible threats and exercise small acts of agency, exploring how conversation—at home, with neighbors, with scientists and policy-makers—shapes the way we live in a world remade by heat.