Dehydration impairs physical performance, impairs judgment, and accelerates the progression to heat illness. By the time a construction worker feels thirsty, they are already 1–2% dehydrated — enough to measurably reduce strength and concentration. On a hot NYC site, proper hydration must be a structured practice, not something left to individual memory.

• 1% dehydration: reduced aerobic capacity and reaction time — you feel it as early fatigue
• 2% dehydration: measurable drop in cognitive performance — your judgment is impaired
• 3–5% dehydration: significant physical and mental decline — early heat illness territory
• Thirst is a lagging indicator — when you feel thirsty, you're already behind on fluid replacement
• Water requirement in heat: 1 cup (8 oz) every 15–20 minutes during work — not just at breaks

• Water: Primary hydration source. Cool (not ice cold) water is absorbed faster than warm or very cold
• Sports drinks: Useful when sweating heavily for more than 1 hour — replaces electrolytes (sodium, potassium) lost in sweat
• Avoid during work hours: Coffee, energy drinks, and alcohol are diuretics — they cause the body to lose more fluid than they supply
• Pre-hydrate: start work well-hydrated. Light yellow urine in the morning = properly hydrated. Dark yellow = already behind