In our culture, we may not typically think of foods as having additional qualities beyond calories and specific nutrients. Traditional Chinese medicine and other ancient modalities such as Ayurveda view foods with qualities including heating or cooling. If you find that the heat of summer is aggravating you emotionally or physically (an example of "heat" in the body might be a hot itchy rash), I suggest incorporating more cooling foods into your routine:
1) Raw foods (such as a salad) are more cooling than cooked foods. Foods that are cooked for longer tend to be more warming.
2) Most fruits and vegetables are cooling, and also cleansing, as many of you know. Ones that are especially cooling include radish, cucumber, zucchini, watermelon, lettuce and most other leafy greens. Vegetables that are warming include garlic, onions, kale, cabbage, mustards, and leeks. Warming fruits include cherries and dates.
3) Gluten-free grains that are cooling include amaranth and millet. Sprouting grains, seeds, or legumes will increase their cooling nature.
4) Most animal foods are neutral or warming. Lamb is warming, as are chicken and beef. Pork is neutral and fish tend to be neutral or cooling, depending on the fish.
For more information on the subject, I suggest consulting the book "Healing with Whole Foods" by Paul Pitchford.