why does Blood Pressure rise when the temperature is hot?

Question

Aren't the blood vessels supposed to dilate and thus cause low blood pressure? I'm a little confused..Enlighten me, please.

Answer 1

You are right about the response of the blood vessels. The blood pressure normally falls when it is hot. Sweating and loss of fluid by evaporation from the skin also causes dehydration and contributes to the low blood pressure.

Answer 2

On a guess? I would say that the larger vessels constrict in order to force blood through the samller vessels near the skin to transfer heat. That constriction causes the increase.