Our bodies need plenty of water year round. We don't always think about drinking since the sun isn't beating down on us, but it's still as important as it would be in July. Simply breathing outside in the cold weather, respiratory fluid loss, causes the body to lose a lot of its water. And those layers that keep you warm also makes the body work harder due to the weight and the ensuing perspiration.
I start my day with a 16.9 fluid ounce bottle of water pretty much prior to doing anything in the morning year round. Then drink water "like its my job" throughout the day. Get in the habit and keep your body functioning properly.
Stay safe, warm and hydrate!