I am an esthetician and I am going to give you a few examples of what can cause dry skin and some tips on how to combat these issues.
First and foremost is not drinking enough water.
Our bodies are made up of mostly water and skin is the largest organ in our body. It is essential that you drink enough water, whether it is cold or hot outside to keep your skin nice and soft. Speaking of hot and cold, heating and air conditioning can both cause dry skin. The winter months can cause lots of dry skin from the frigid temperatures to being inside with heat all day. You may notice that when you spend a lot of time in central heating your skin and lips dry out. To combat this issue, make sure you use extra moisturizer. My favorite moisturizers for the winter months and central heating are thick and unscented creams. You may also notice that in the summer months when you want to show off your skin, the central air conditioning is making your skin dry. Being out in the sun can also contribute to dry skin. There are a few ways you can deal with this issue. Just like dealing with dry skin from central heat, you can use a moisturizer (maybe use a lighter one in the summer) on your hands, feet, and lips or any other dry spots. In addition to moisturizer, you can purchase a humidifier for your home. You may not feel like adding humidity in the summer, but you can just put this in your bedroom if you would like to help your dry skin.