Without a humidifier, you can actually feel the dry air and it gets pretty uncomfortable at night. The skin looks dry and flaky in the morning. If you happen to catch a cold, your symptoms get worse because your mucus tends to dry out (the only remedy is to then go and stand in a high humidity bathroom for some-time or inhale vapors. You need it for at-least 2-3 peak winter months in the eastern part of the US.