The official recommendation is "fluid", not specifically water. I'm not referring to Medifast recommendations, just to the medical professionals. The recommendation for xx glasses of "water" dates back to a time when it was believed easier to just say water than to try to explain what all counted as fluid. The body recognizes fluid content in water and flavored water the same way, and it also recognizes the fluid content in fruit and other foods.
I love water, and agree that warm weather helps us drink more. I keep a glass jug of filtered water in the fridge at all times. Tastes fantastic that way