Without enough water, your body cannot properly sweat and as a result, your core temperature increases, which can make you feel hot.
Minagawa says dehydration occurs largely because of a decrease in the volume of plasma—which is the liquid part of the blood that contains proteins
In response to the rise in internal body temperature, a decrease in blood pressure, and an increase in heart rate, you could become nauseous or even begin throwing up.
Sweating may cause a decrease in both plasma volume and electrolyte levels (think sodium and potassium), which is associated with exercise-induced muscle cramps.
Water helps to move food along through your gastrointestinal system. A deficit in water could cause you to feel backed up.
If you're someone who repeatedly has kidney stones or UTIs, it's likely you aren't drinking enough water to flush out bacteria and stone-forming minerals.
"Hydration status and the fluid in the lungs and airway play an important role in proper airway clearance," she says.
Avoid all of these side effects by carrying around a reusable water bottle with you this summer, although, there are plenty of other ways you can stay hydrated aside from drinking water alone.
"Smoothies, soups, milk, fruits are also a great source of fluids," says Minagawa.