For most everyday humidifiers, the answer is simple: use cool, distilled, or demineralized water. Think of it like making a glass of iced tea—you wouldn’t use hot tap water if you wanted it crisp and refreshing. Your humidifier feels the same way.
But wait—there’s a twist. Some humidifiers are designed to warm water. The key is reading your manual, which I know sounds about as fun as flossing, but trust me, it saves headaches later.