Catastrophic weather can affect individuals unequally and lead to episodic selection, but the effects of weather events are rarely documented. In August 2015, a nighttime thunderstorm led to the deaths of hundreds of purple martins (Progne subis) roosting in downtown Tulsa, Tulsa County, Oklahoma. We compared samples of birds dying to those that survived, and we found nonrandom mortality based on age and sex. Yearling females were overrepresented among the dead, and juveniles were overrepresented among the survivors. The results could reflect differences in where birds were in the roost, and they suggest the potential for age- or sex-based selection on perch preference, dominance, or migratory phenology.