In mountains, cold dry air extracts water from your body during winter like hot humid air does in summer. But the former does it faster than the later. The body has a number of ways to communicate this loss of its major constituent. That accounts for about 50-60% of the total body weight.
The first one is simple, thirst. Drink water often to avoid thirst.
The second one is chapped and dry lips that are pampered with frequent dash of chapsticks and / or lip balms while trekking. This pampering is a temporary measure and not very helpful for your body. Because the body needs water instead of grease packed in these cosmetics. But it is definitely helpful for the cosmetic manufacturer!
Drink water as often as you apply lip softeners. Your body will express gratitude and the lips will be supple without any special efforts.
The third one is dark yellow urine. Normally, the urine looks pale yellow because the fluids, including water, dilute the yellow pigments found in the urine. So if you drink less water, concentration of the pigment in the urine will increase and the color will change accordingly. Remember, the color of urine sometimes indicate serious diseases. If hydration does not improve the color of the urine, you must visit your doctor.
If you ignore these simple signs of dehydration, the situation aggravates and affects your performance on the slopes. For example, a dehydrated trekker may feel:
So, next time you go on a mountain trek, do watch your body and first help yourself and then the manufacturers. You may also experience these dehydration signs in daily life. Be watchful and have enough water every day!