When the mercury hits 90 and above, tempers can get pretty fired up, too. But another glass of water or a slice of watermelon might help, because irritability is a classic side effect of dehydration.
The first physical sign is thirst, of course. But other symptoms are more subtle. You might get a headache. You can become cranky, forgetful, tired and dizzy, and your skin appears dry and wrinkly.
Remember the old adage to drink eight glasses of water a day? Well, in 2004, the Institute of Medicine issued new general fluid recommendations indicating women should drink 11 cups per day and men 15 cups.
These amounts include the water in all food and beverages we consume. Iced tea, fruit juice and even hot coffee and soups all count as hydrators. It turns out that 80 percent of our water intake is from drinking water and other beverages, and the other 20 percent is from food.