If you are struggling to sleep during warm weather, having your fan on can be beneficial to your sleep. If you are concerned about this, you can also look for fans with built-in timers. These fans will automatically turn off at a specified time.  However, having a fan on for a long period of time will use up a lot of energy. This will add to the cost of your fan. In addition, some studies have found that having fans on for prolonged periods can dry out your skin. If you do suffer from these symptoms, you can use a moisturizer on your skin.