Thirst is just one symptom that can appear in a variety of diseases. There are many diseases in which one feels thirsty. When the weather is hot, physical labor, blood loss, burns, vomiting, diarrhea, high temperature, heat stroke and a lot of heat release, one can feel thirsty, which is caused by a severe lack of water in the body and often results in dry mouth, haggard face, collapsed eye sockets, and dry skin that does not stretch.
Diabetes, uremia, hyperthyroidism, kidney disease, and improper use of medications can all cause dry mouth and thirst.