If you are like many people, myself included, it's hard to remember to drink enough fluids when you're not hot. Most of us remember that if we're exerting our bodies physically, we need to replenish them with water, tea, or other beverages; but when temperatures drop and we find ourselves shivering our way into work, hydration is not quite so intuitive. The fact is, however, that the white mist you breathe out is actually water vapor: you lose just as much water in the winter as you do during the summer!
Dehydration is no laughing matter, either. It can cause you to become more susceptible to falling ill and can even cause you to gain weight: the symptoms of dehydration can mimic those of hunger, causing you to overindulge when you're not really hungry at all; you're thirsty (source).
A good rule of thumb is that you should drink half your weight, in pounds, in ounces of water. If you weigh 150lbs, you should be drinking 75 ounces of water, or other beverages like tea, per day, year-round. If you exercise, you should be drinking even more water than that!
Of course, it can be difficult to drink that much plain water each day, so why not give yourself an incentive to drink more fluids by drinking more tea? Brew a cup in the morning; bring a thermos with you to work; and drink a cup with dinner and after dinner. I like to indulge in rooibos blends, because I don't have to worry that caffeine is causing me to lose -- and need to replace -- even more water.
The elderly are particularly susceptible to dehydration: According to a study conducted by the NIH in 1991, 6.7% of Medicare hospitalizations were at least partially due to dehydration (http://www.ncbi.nlm.nih.gov/pubmed/8059883). Make sure your elderly loved ones have access to a wide variety of teas and other beverages to appeal to their taste buds and ensure they remain adequately hydrated! With the holidays drawing near, it may be a great time to stock your grandparents, parents, and aunts or uncles up with teaware, tea brewing accessories, and new tea blends.