Cooling Herb Blend
Realistically any good cooling tea blend needs a blend of refrigerants (herbs that cool the body down) and diaphortetics (herbs that make you sweat) So, my suggestion is to pick and choose a few flavors you like from each category to make a big batch of tea you can keep in your fridge for those super hot days!
My favorite refrigerants: Lavender, Spearmint, lemon balm, hibiscus,
My favorite cooling diaphoretics: Peppermint, chamomile, lemon balm
Honestly I usually mix all of these with an emphasis on the lemon balm and mint and steep for at least 30 min before cooling and serving over ice.