Why do people feel thirsty and need to drink cool water after taking hot shower/bath?

Answer 1

Hot water actually dries out your skin. Heat (in any form) causes your body's cells to speed up their activity and heat extrapolates water from the human body. Plus, your brain will send messages to your body to cool off and one way that we've all learned to cool off is to put something cold on ourselves or have something cold to drink.

Answer 2

Because you get hot when your in hot water so you feel thirsty.