Why do phone batteries drop faster during summers?
Batteries of both Android and iPhones are powered by lithium-ion cells, which are sensitive to temperature changes, especially heat. During summers, when phones heat up, chemical reactions inside the lithium-ion cells speed up, which damages the batteries' overall capacity to hold charge in long-run. Apple and other smartphone makers hence suggest 0ºC-35ºC temp range as optimum for phone usage.