1. Oppressively hot and humid weather
   "The sultriness of the tropical night made it difficult to sleep"
    
2. The quality of expressing or arousing sexual desire
   "the sultriness of her look was unmistakable"; "the sultriness of lust was in the air"

Type of: atmospheric condition, conditions, desirability, desirableness, oomph [informal], sex appeal, umph [informal], weather, weather condition