Question

Explain why people prespire a lot on a hot humid day

Answer 1

It's excretion of fluid by the body that evaporates immediately and thereby serves as a means to regulate body temperature. ... - On hot humid days, water is evaporated slowly, thus more of this sweat is retained

Answer 2

In humid conditions where surrounding air cannot hold further water vapour, sweat evaporates slowly, if at all. As a result the body heats up. it is difficult for the sweat to evaporate and in high humidity conditions we tend to sweat more. This explains why it feels so much hotter in high humidity.