We estimate how acute air pollution exposure from wildfire smoke impacts human health in the U.S., allowing for nonlinear effects. Wildfire smoke is pervasive and produces air quality shocks of varying intensity, depending on wind patterns and plume thickness. Using administrative Medicare records for 2007?2019, we estimate that wildfire smoke accounts for 18% of ambient PM2.5 concentrations, 0.42% of deaths, and 0.69% of emergency room visits among adults aged 65 and over. Smaller pollution shocks have outsized health impacts, indicating significant health benefits from improving air quality, even in areas meeting current regulatory standards.