Most people know to drink lots of water during the hot summer months. However, now that it is winter that doesn't mean that you do not need to drink as much water. During the winter, the humidity level is much lower. Also, most heat sources (forced hot air, circulated hot water, electric) will lower the humidity level. This causes you to lose moisture through the skin and through your breath. You will be less aware of your water losses because you are not sweating or exercising.
Another source of dehydration that is overlooked is flying. Now that it is the holidays, many of us will be flying to visit family and friends. A comfortable level of humidity is about 50%. An airplane will generally start out at 25% humidity and sometimes will drop to almost undetectable levels. Drinking some type of fluid every hour on the flight will help you feel much better when you reach your destination. If it is a long flight, you may even want to put a little sesame or almond oil in your nasal passages to avoid the uncomfortable itchy nose that develops from excessive dryness. Despite common belief, you are not prone to getting a common cold with dry mucus membranes.
It cannot be said enough: just about everyone needs to drink more water. You do not necessarily need the recommended 8- 10 glasses a day. However, waiting until you are thirsty is not a good idea. Being dehydrated can cause fatigue, headache, and muscle soreness. Being dehydrated also makes it harder to lose weight and may lead to obesity. You do not need to drink just water during the day. You may increase your fluid intake by eating more fruits and vegetables. Also, any kind of fluid will suffice. A word of caution about sodas: the non-diet type should be strictly limited because of the amount of sugar. All sodas should be limited if you tend to have kidney stones because the citrate and phosphorous in the sodas can precipitate kidney stones.