Hydration in Summer: It Is More Complex Than You Think

Staying hydrated in summer seems like simple advice — drink more water — but the physiology of hydration is genuinely more nuanced than that, and understanding it can make a meaningful difference in how you feel and perform on hot days. Hydration is not just about water volume; it is about electrolyte balance — specifically sodium, potassium, magnesium and chloride — which regulate fluid distribution between cells and circulation. Drinking large amounts of plain water while sweating heavily can actually dilute electrolyte concentrations, causing a condition called hyponatremia that can impair cognitive function and energy.

For most people engaged in moderate summer activity, adequate hydration comes from a combination of water, electrolyte-containing foods and avoiding excessive alcohol and caffeine, which promote diuresis. Excellent food sources of hydration include cucumbers (96% water), watermelon (92% water), strawberries (91%), celery (95%), bell peppers (92%) and lettuce (96%) — all of which are abundant in summer and provide minerals alongside fluid. For those exercising intensely for more than 60 minutes in heat, a beverage containing sodium and potassium will support better hydration than water alone.

Thirst is a reliable but imperfect hydration cue — by the time you feel thirsty, you are likely already mildly dehydrated. A more reliable indicator is urine color: pale yellow indicates good hydration, while dark yellow signals a need for more fluid. Older adults have a blunted thirst response and are at higher risk for dehydration — a reminder for family members caring for elderly parents in the summer heat. At NutriGreene, we incorporate hydration counseling into all of our nutrition consultations because it affects everything from energy to digestion to skin health.

Sources

• Popkin BM, D’Anci KE, Rosenberg IH. Water, hydration and health. Nutr Rev. 2010;68(8):439-458.

• Casa DJ, et al. National Athletic Trainers’ Association position statement: exertional heat illnesses. J Athl Train. 2015;50(9):986-1000.

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