Humans have a core body temperature of about 37^oC.
They gain energy from constrictdilateevaporatesevaporationfaeceslessrespirationrespireshiver which releases heat, and from their surroundings on hot days.
They lose heat energy of their surroundings are cold, and also through urine and constrictdilateevaporatesevaporationfaeceslessrespirationrespireshiver. Evaporation can also cool the body down.

When it is hot, your blood vessels near the surface of the skin constrictdilateevaporatesevaporationfaeceslessrespirationrespireshiver and your skin goes pink. Energy is passed from the blood to the air.
You can also use hats and the shade to stay out of the hot sun, use a fan to increase constrictdilateevaporatesevaporationfaeceslessrespirationrespireshiver or use cold drinks.
When you are hot you sweat - this constrictdilateevaporatesevaporationfaeceslessrespirationrespireshiver off your skin and transfers energy away from the blood and body.


When you are cold you constrictdilateevaporatesevaporationfaeceslessrespirationrespireshiver - this makes the muscles move and constrictdilateevaporatesevaporationfaeceslessrespirationrespireshiver more - releasing more heat energy through respiration.
When it is cold, the blood vessels constrictdilateevaporatesevaporationfaeceslessrespirationrespireshiver and less blood reaches the skin surface. The means that constrictdilateevaporatesevaporationfaeceslessrespirationrespireshiver energy is transferred to the air.
You can also eat or drink warm foods to warm yourself up or put on warmer clothes.