That line is really important in this context because evaporation functionally doesn't happen at 100% humidity because the air is already saturated with water (I think technically evaporation still happens but only very little). If it's really hot but still sub 100% humidity, your sweat still functions, even if it really works best in dry heat. Past that, it stops helping and you're just soaked in hot sweat that accumulates.
You won't just drop dead, but barring some other actually effective means of cooling yourself, you will overheat and die in those conditions.
Close to it, but sure, not exactly 100%.
That line is really important in this context because evaporation functionally doesn't happen at 100% humidity because the air is already saturated with water (I think technically evaporation still happens but only very little). If it's really hot but still sub 100% humidity, your sweat still functions, even if it really works best in dry heat. Past that, it stops helping and you're just soaked in hot sweat that accumulates.
You won't just drop dead, but barring some other actually effective means of cooling yourself, you will overheat and die in those conditions.