One way to boost your ability to fight of the flu and the common cold during the winter months is to stay hydrated. You may have never thought about it but dehydration happens just as easily in the cold of winter as in the heat of summer. We may not notice that we sweat as much during the winter because sweat will evaporate quicker in cold air. Our body is also losing water through breathing, and when it’s cold outside you can see this as water vapor when you exhale.