Can occur when a person fails to increase fluid intake appropriately when exercising for the first time in a hot climate

Multiple things can occur to a person who fails to increase hydration while in a hot climate. The first and most obvious of these would be dehydration, which also leads to the second and very probable reaction, heat stroke. Ultimately, it depends completely on the exercise that the person is attempting. For example, a runner who fails to hydrate properly would be a more likely candidate to skip over dehydration and suffer a heat stroke.

If it doesn't have a nucleus its a prokaryote