The company my Dad worked for in the 1990s had a really brilliant idea that went on: Have many of the annual conferences in New Orleans in July or August. If I remember correctly is that he told me most days you could barely step outside (that the heat and humidity was that oppressive for the uninitiated at that time of the year).
Your dad is right. Heat index here today 112. Very high humidity. Feels likr the 90s at nite. Even ac running continuously cant get home cooler than near 80. Should have let it all go back to the alligators after Katrina,IMO.