What is the ideal room temperature for sleep?

Around 18–20°C (65–68°F) for most people. Core body temperature must drop to initiate sleep, which is also why a warm shower an hour before bed helps — the subsequent heat loss aids sleep onset.

Around 18-20°C is ideal, but the principle is falling core temperature — cotton bedding, a fan for air movement, and a cooler shower an hour before bed help when AC is not an option.

Heat disrupts deep sleep and REM disproportionately, which is why hot nights feel unrefreshing even when total hours are unchanged.