Dry air sucks water out of the skin. Consider using a good moisturizer to keep moisture from leaving your skin. Also consider using a humidifier in your home. During the winter, heated indoor air can be very dry. During the summer, air cooled with an air conditioner can also be very dry.
Another relevant factor is the amount of time your skin is directly exposed to water. Although you might think this is a good thing, it may not be. Hot showers and baths remove oils from the skin that help hold in moisture.
Do you frequently take hot baths or showers?