Use your body super abilities. It can produce heat for short time (enough for moisturising, soaping, and rinse). After cold shower use your towel strongly to obtain warm. This kind of russian SPA is extremly useful for skincare. Think about it as a kind of yoga, it provides good better circulation in cappilary, makes you healthier. When you turn on water, don't forget to shout "Oh my God!", this short prayer really helps.