It’s an all-too-familiar feeling. You spend the first day of your sun-drenched, flip-flop-wearing vacation feeling dry, foggy, and tired. Jet lag , you assume. But in reality, it's the first signs of dehydration setting in after the flight and sudden heat exposure has begun to soak up your body’s natural moisture. Get to day three of your trip, and if you haven’t been replacing the lost fluids and electrolytes, the dehydration is now beginning to show up in your skin, never mind the dull headache and a general sense of exhaustion. That’s because, when temperatures are scorching , your body begins losing minerals quickly, and your regular eight glasses of water aren’t enough to replenish them. But how much extra water do you really need to drink when visiting a hot country? We’ve spoken to medical professionals to find out.…