The ideal indoor humidity levels in your home should range from between 30 percent to 50 percent (relative humidity) depending on the season and personal preference. In the winter, indoor humidity should be approximately 20% to 40% . The goal is to be between 35 percent and 40 percent. Health experts agree that this is a comfortable humidity level for pets as well. Cold, moisture-laden air finds its way indoors through cracks and drafty doors and windows, and condensing on the surfaces, as it clashes with the warmer air indoors. Therefore, it is important to maintain proper humidity levels in your home during the winter months to avoid dry air, which can cause static electricity build-up, dry, itchy skin, and eyes, the spread of viruses and bacteria, and damage to wood floors, furniture, and musical instruments.