Water and remaining hydrated is imperative for our health. Not only on hot days but for our kidney health, to lower our blood pressure, to remove toxins and to prevent fainting in the hot, summer weather. Lack of water can make you feel dizzy and fatigued. You may also find that you have a headache. It can cause problems with your digestive system and long-term effects can cause a range of health issues. There is a long list of how it can damage your health.