Me last year in Bora Bora drinking coconut water straight from the source
For most of the country, and here in Indiana, the temperatures this summer have been above average. Water is important to the body at all times, but it is especially important in warm weather to keep your body from overheating. Even mild dehydration can drain your energy and make you tired. There are more serious complications with severe dehydration. (Also, sometimes when you think you are hungry, you are really just thirsty!)
So how much water do you need? Studies vary and it depends on how active you are, your health and even where you live. A very general estimate given by The Institute of Medicine is 13 cups for men and 9 cups for women. This isn't too far off from the common advice of at least eight, eight ounce glasses a day. Obviously, the amount you need will vary from person to person and depends on how active you are that day and how hot it is. I think the eight glasses of 8 ounces is a good general rule for regular conditions and more than that if you are working out and/or it is hot.
Water isn't the only thing that hydrates but it is the best option. I'm lucky that I like water and drink it all day but I know some don't like to drink water. My advice, start with just two bottles of water a day - sip it throughout the day. You'll get used to it and maybe even feel more energy because you are better hydrated. If you really can't stand water, add some fruit to it to infuse the fruit flavor into the water.
If you are exercising, water is all you need if you are working out for an hour or less. If you are working out longer than an hour, or you will be out in the sun for more than a few hours, you might need something more than water that will help to replenish your sodium and potassium levels which are lost through perspiration. A sports drink is an option (please look for one without artificial sweeteners and fewer chemicals!!!) or coconut water is a great sports drink alternative. Coconut has fewer calories, fewer sugar, less sodium and more potassium than any sports drink plus it is all natural (make sure you look at the label if you are buying it packaged). Both sports drinks and coconut water have lots of sugar though so don't go overboard with either.
Alcoholic and caffeinated beverages, such as coffee, teas, and colas, are not recommended for optimal hydration. These fluids tend to pull water from the body and promote dehydration. Fruit juice and fruit drinks may have too many carbohydrates (sugar), too little sodium, and may upset the stomach. If you're going to drink fruit juices while exercising, you may try diluting them with 50% fruit juice and 50% water first.
Adequate hydration will keep your summer activities safer and much more enjoyable.
References: The Cleveland Clinic, Mayo Clinic, WebMd