B Brian wrote:
Rain and humidity get absorbed into the skin. This adds to you water intake and will affect your output too.
That's wrong. Almost no rain or humidity is absorbed through your skin. Your outermost layer of skin is made of highly keratinized, squamous epithelial cells, sealed together with lipids secreted from lammelar bodies (a specific organelle) during apoptosis (programmed cell death). High humidity decreases evaporation, which has a minor influence on eccrine gland secretion, and interstitial fluid loss. Most sweat loss it due to body temperature homeostasis, not fluctuations in humidity.
B Brian wrote:
Conversely, cold increases your blood circulation so the body can heat its self more.
Also not true. Cold weather decreases circulation, to conserve warmth in the body core. That's why extremities (fingers, toes, etc.; not the other male extremity) tend to shrink in the cold, decreased blood flow. However, extreme cold reduces the humidity in the air, which increases moisture lost during respiration, and can, in fact, dehydrate you.