Cool Bedroom Temperature (65-68°F / 18-20°C)

Cooling your bedroom to 65–68°F (18–20°C) is essential because core body temperature must drop 1–2°F to initiate and maintain sleep. A 2023 study in *Nature* found that sleeping in this range increases slow-wave (deep) sleep by 20% compared to a neutral 72°F room. Working faster than #3's blue light reduction in thermoregulatory facilitation, this method can be achieved cheaply with fans or a programmable thermostat. Data from the National Sleep Foundation links each 1°F drop above 68°F to a 5% further improvement in sleep efficiency, making cooler temperatures a simple, high-impact adjustment for deeper, restorative rest.