Why: It's low in calories, not too expensive and 92 percent water, which quenches your thirst and fills you up on a hot summer day.
Health Perks: Watermelon has 7.5 to 10 milligrams of the antioxidant lycopene—believed to guard against heart disease and some cancers—per cup. That's about 40 percent more than is found in raw tomatoes (cooked tomatoes have more). It's a good source of vitamins A and C. It also contains potassium, vitamin B6 and thiamin. Plus, it has citrulline, an amino acid that may help reduce the risk of cardiovascular disease, stimulate the immune system, and accelerate the healing of wounds.
Nutrition: Serving size: 1 cup, diced (152g), calories 46, total fat 0.2 grams, cholesterol 0 milligrams, sodium 2 milligrams, total carbohydrate 11.5 grams, dietary fiber 0.6 grams, sugars 9.4 grams, protein 0.9 grams.
Seek Out: Firm, juicy, red flesh without white streaks and a rind free of cracks, bruises or mold. The seeds should be dark brown or black. According to James Parker, global produce coordinator for Whole Foods Market, "Look for melons that have a uniform shape (not small on one end and larger on the other). Ripe fruit will have a slight give on the end opposite to the stem and a slight yellowing of the rind on the lightest part of the outside."
If you can't cut a plug and peek inside (the best way to see if it's ripe), Peter Romano, the produce director at New York City's famed Fairway Market, says you can tap the melon in the middle with your palm: If it's ripe, you should hear a hollow sound.
Avoid: Pale flesh, white streaks and whitish seeds (if you can peek inside). The rind should be free of bruises, soft spots or mold. "And make sure there are no splits, veins, hollow pockets, dark red streaks or blood-red (as opposed to fire-engine-red) color," says Romano.
Storage: According to chef Aliza Green, chef and author, ripe watermelon will keep best (for about five days) if cut up, covered with plastic wrap and refrigerated.
Interesting: Watermelon is also a vegetable—a relative of the pumpkin and squash family.