The hot weather of summer, when drinking lots of fluids is required, is best suited to the refreshing, slightly astringent taste of green teas – which are also great to drink iced. Green tea is also rich in vitamins, amino acids and minerals, so not only does it have a great refreshing affect in hot weather, it also keeps your body healthy in this season when you're likely to be more active. Green tea is best drunk during, or immediately after, a meal or with food, as it can cause some stomach upsets on an empty stomach, especially for people who rarely drink teas.
Except green tea, fruit teas are also another good choice for summer. You can enjoy it either hot or iced. But I think it will be more enjoyable for iced!