What is the difference between warm mist and cool mist humidifiers?

Warm Mist Humidifiers are more frequently used in the winter. The warm mist helps maintain a warmer temperature in your home during the winter months. 

Cool Mist Humidifiers expel a mist that is room temperature. Although the mist and moisture being distributed is not cold, it may help decrease the temperature in the room that it is in, only by a few degrees.