The Sleep Foundation puts the best bedroom temperature for adult sleep at roughly 65 to 68°F (about 18 to 20°C). The range works with the body's own overnight temperature drop rather than against it.
Core body temperature is not fixed. It hovers near 98.6°F and falls by roughly 2°F across the night, beginning about two hours before sleep and reaching its low point in early morning. A warm room blunts that drop.
Blunting the drop matters because it delays and shortens slow-wave sleep, the deep stage tied to memory consolidation, immune function and physical repair.
What the research shows about heat
A widely cited 2012 review in the Journal of Physiological Anthropology concluded that "the stereotypical effects of heat or cold exposure are increased wakefulness and decreased rapid eye movement sleep and slow wave sleep."
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Under realistic bedroom conditions with normal bedding and sleepwear, heat exposure specifically raises wakefulness and cuts into slow-wave and REM sleep, the authors wrote. Humid heat is worse than dry heat.
Slow-wave sleep and REM are not interchangeable. A 2025 commentary in the journal SLEEP noted that the coupling of sleep spindles with slow oscillations in non-REM sleep supports memory consolidation, especially episodic memory.
Fragmenting those stages by overheating the bedroom chips away at the very sleep that stitches new memories together.
Practical numbers and how individuals differ
Michelle Drerup, PsyD, a sleep psychologist at the Cleveland Clinic, sets the adult range slightly lower, at about 60 to 67°F. "Heat is a huge disruptor for REM sleep," she said, adding that a room that becomes uncomfortably hot or cold makes waking more likely.
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The exact number is personal. Bedding, sleepwear, humidity and age all shift the sweet spot. Infants and toddlers generally do better slightly warmer, around 65 to 70°F, because their bodies are less able to regulate temperature.
Why it can feel different after 50
Older adults do not always fit the standard adult numbers. A 2023 study of 50 community-dwelling older adults, published in Science of the Total Environment, tracked nearly 11,000 nights and found sleep was most restful when nighttime bedroom temperature stayed between 68 and 77°F.
Sleep efficiency dropped 5 to 10 percent as temperatures climbed from 77°F to 86°F. Individual differences were large.
Lead author Amir Baniassadi, PhD, of the Hinda and Arthur Marcus Institute for Aging Research at Hebrew SeniorLife and Harvard Medical School, framed the takeaway this way. "These results highlight the potential to enhance sleep quality in older adults by optimizing home thermal environments and emphasizing the importance of personalized temperature adjustments based on individual needs and circumstances."
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What to try tonight
If the bedroom feels warm, the simplest interventions match the physiology. Lower the thermostat a few degrees before bed. Swap heavy bedding for lighter, breathable layers.
A warm shower an hour or two before sleep can help, somewhat paradoxically. It pulls blood to the skin and speeds the core-temperature drop that follows.
For shared beds with different preferences, separate blankets and cooler sleepwear for the warmer sleeper can bridge the gap. In hot climates or during heat waves, fans, cross-ventilation and blinds drawn by day help hold nighttime temperatures closer to the ranges the research supports.
Anyone with persistent insomnia, loud snoring or breathing pauses at night should talk to a doctor. A cool bedroom is a foundation, not a cure.
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