Quick answer: The best temperature for sleep is a comfortably cool room. Rest's program starts its users at 65 to 68°F (18 to 20°C) with 70°F as the upper limit. In lab studies, a warm room means more time awake and less deep sleep, while a cold room barely changes sleep once you have a blanket to cover you. The only study that measured real bedrooms, in older adults, found sleep stayed efficient up to about 77°F. A hot room can wake you, but it is rarely what keeps insomnia going.
You have tried it both ways. Thermostat down, and you are shivering at 2am with the covers up to your chin. Thermostat up, and you are awake at 3am with one leg out from under the duvet, flipping the pillow to the cool side. Someone told you 65°F, someone else swears by 60, and your partner would like a word about both.
So what is the best temperature for sleep? Comfortably cool. Rest's program puts it at 65 to 68°F and treats 70°F as the upper limit. Cool works not because it feels nice, but because of how sleep starts: a drop in core body temperature. A 2019 review of the temperature dependence of sleep even argues that the moment you are most likely to fall asleep is when your core temperature is falling fastest [1].
What Is the Best Temperature for Sleep?
Rest's program answers 65 to 68°F, and not above 70°F. Those are the numbers the program gives its users rather than thresholds any single trial fixed. While the research behind a cool bedroom has two parts, neither one hands you a perfect thermostat setting.
The first is what happens in a lab. A review of laboratory sleep studies found that once people have bedding and pajamas, heat is what hurts: a hot room means more time awake and less deep sleep and rapid eye movement (REM) sleep, and humid heat makes it worse. A cold room leaves sleep stages mostly unchanged, because the blanket does the buffering, though cold still changed how the heart behaved during sleep, so cold is not free either [2].
The second is what happens in the real world. In the largest sleep-tracker dataset yet used to answer the question, researchers matched about seven million wristband sleep records from 47,628 adults in 68 countries to the local outdoor weather. Warmer nights meant shorter sleep, mostly because people fell asleep later; the loss steepened once outdoor nighttime lows passed about 50°F (10°C), and on nights above 86°F (30°C) people lost around 14 minutes. Those living in hot regions lost more sleep per degree, not less, which points to little or no adaptation [3]. The study measured the weather outside, not the bedroom, so it tells you that hot nights cost sleep, not what to set your thermostat to.
The range is wide because people differ. The one study that put temperature sensors in real bedrooms followed older adults living at home, and their sleep was most efficient between 68 and 77°F (20 to 25°C); efficiency fell 5 to 10% as the room warmed from 77 to 86°F, with big differences from one person to the next [4]. That band sits above Rest's starting range and comes from older adults only, but it makes the same point from the other side: the losses began once the room passed the upper 70s, not when it moved a couple of degrees inside the cool range. The point where the room stops being cool matters more than the exact number of degrees.
Why a Cool Room Helps You Fall Asleep
Your core body temperature follows a daily rhythm, and sleep comes most easily while that temperature is on its way down to its overnight low [1]. The heat leaving your body has to go somewhere. It leaves through your skin, mostly your hands and feet, where blood vessels widen and release warmth into the air.
That is why warm feet predict fast sleep. In a Basel study, the temperature gap between the hands and feet and the trunk was a better predictor of how fast people fell asleep than core temperature, melatonin, heart rate, or how sleepy they said they felt [5]. More blood in the feet meant more heat leaving the body and a shorter wait for sleep.
Cool air and warm feet work together: your feet release the heat, and the room has to be cool enough to take it. If the air is nearly as warm as your skin, the heat has nowhere to go and your core stays high. If the room is cold, the blanket traps a layer of warm air against your skin. Your hands and feet stay warm enough for their blood vessels to stay open, so your core keeps shedding heat into that layer, which slowly leaks it to the room [2]. That layer is not a side effect.
The 2019 review argues that the warm microclimate people build with bedding, the way animals build nests, is part of what triggers non-REM sleep, and that the drop in core temperature may partly follow from the widened blood vessels rather than cause sleep on its own [1].
So the target is cool air around a warm bed, not a cold room.
Cool Room, Warm Feet: How to Set Up Your Bedroom
Start at 65 to 68°F, with 70°F as the upper limit. Those are Rest's program numbers; within that band, go with whatever you sleep best at. If you cannot cool the room that far, Rest's program suggests a fan for air movement, leaving the bedroom door open, closing the blinds on hot days so the room does not store heat, and switching to breathable cotton sheets and pajamas.
Take a warm shower or bath one to two hours before bed. It sounds backwards. Warm water pulls blood to your hands and feet, and the heat loss that follows drops your core temperature faster. In a 2019 meta-analysis of 13 studies, water at 104 to 109°F (40 to 42.5°C), for as little as 10 minutes and scheduled one to two hours before bed, shortened the time to fall asleep and improved sleep efficiency [6]. That one-to-two-hour window is where the evidence was strongest; the authors say the ideal timing is not settled.
Warm your feet. The direct evidence is small but points one way. In a laboratory study, six young men slept in a 73°F (23°C) room with and without bed socks; with socks they fell asleep about 7.5 minutes sooner, slept 32 minutes longer, and woke less often, with no change in core temperature [7]. Skin warming also works on a larger scale and even after you are asleep: when researchers warmed people's skin by 0.4°C (less than a degree Fahrenheit) with a temperature-controlled suit, without changing core temperature, they spent less of the night awake and more of it in deep sleep. The effect was strongest in older adults, with and without insomnia, whose probability of an early-morning waking fell from 0.58 to 0.04 [8]. If socks make you feel too hot, just skip them.
Share the bed, split the bedding. Two people rarely want the same room, and the evidence settles who gets the thermostat: cold is the problem bedding can fix, heat is the one it can't, so set the room for whoever runs hot and let the other person add a layer.
Is Your Bedroom Temperature Causing Your Insomnia?
A hot room can wake you. It rarely explains insomnia that has lasted months.
Insomnia has been linked to body temperature patterns. Trouble falling asleep is associated with a core temperature rhythm that runs late, so people are trying to sleep while their body is still in its evening "wake maintenance zone," and waking repeatedly is associated with a higher core temperature through the night [9]. Those patterns sit in the body's rhythm, not in the room. The thermostat can help the heat leave, but it cannot move the rhythm, and it cannot undo what months of lying awake have taught your brain about the bed.
That is the limit of sleep-hygiene fixes. Setting the room to 66°F is worth doing, and it will not on its own turn around sleep that has been off for months. Reviews of the evidence find sleep hygiene alone a weak treatment for a clinical sleep disorder [10], and the American Academy of Sleep Medicine (AASM) advises clinicians not to use it as a stand-alone therapy [11]. What the AASM strongly recommends is CBT-I (Cognitive Behavioral Therapy for Insomnia), the first-line treatment for chronic insomnia in adults [11]. CBT-I works on what keeps insomnia going once it has started: a wake time that moves around, too many hours in bed, and a bed your brain has learned to associate with being awake.
Rest is a program built on the behavioral principles of CBT-I, plus circadian biology and neuroscience, developed together with world-class sleep experts from institutions like UCSF and Stanford. Bedroom temperature is one line in its setup. The daily work is the morning check-in, where the coach reads last night's sleep log and adjusts your sleep window, and the coach is there by text or voice at any hour when a night goes wrong. If your schedule has drifted late, the place to start is the wake time, not the thermostat, and How to Reset Your Sleep Schedule walks through how.
Cool the room. Then, if your sleep has been off for months, see how Rest can help »
Frequently Asked Questions
Is 72°F too hot for sleeping? 72°F is warmer than the 65 to 68°F range Rest's program recommends, and above its 70°F upper limit. It is not a disaster: in-home research on older adults found sleep still efficient up to about 77°F, with the losses starting above that [4]. If 72°F is as low as your thermostat goes, a fan, cotton bedding, and a lighter duvet make up some of the difference.
Is it better to sleep in a cold room or a warm room? Comfortably cool beats both. With bedding and pajamas, a warm room means more time awake and less deep and REM sleep, while a cold room leaves sleep stages mostly unchanged because the blanket buffers it. Cold is not free, though: the same review found it shifts heart-rate control during sleep, and you wake up to pull the covers back on [2]. Keep the air cool and fix a cold room with bedding, not by turning the heat up.
Does wearing socks to bed help you fall asleep? Socks can help, even if the direct evidence is small. In one laboratory study of six young men sleeping in a 73°F room, bed socks cut the time to fall asleep by about 7.5 minutes and reduced awakenings [7]. The mechanism is the one behind warm feet in general: heat leaving through the hands and feet predicted faster sleep onset in earlier laboratory work [5]. If socks make you feel overheated, skip them; a warm shower one to two hours before bed works on the same principle.
Why do I wake up hot in the middle of the night? Check the room first, since heat is what disrupts sleep stages once you have a blanket [2]. If the room is cool and you still wake up sweating, and you are a woman in your forties or fifties, hot flashes are a likely reason: in a study of 168 midlife women wearing monitors that detect hot flashes objectively, a wake episode coincided with 78% of the nighttime flashes recorded [12]. Why menopause steals your sleep explains what is happening and what helps. Whatever the trigger, what you do once you are awake matters as much as the cause, and what to do when you can't get back to sleep at 3am covers that part.
Disclaimer. This article is published for general information only. It is not medical advice or a diagnosis, and nothing here is a recommendation to take, avoid, or change any supplement or medication. Rest is not a substitute for professional medical care. Do not start, stop, or adjust a treatment, including a prescribed sleep medication, without talking to your clinician.
Citations
Harding, E. C., Franks, N. P., & Wisden, W. (2019). The temperature dependence of sleep. Frontiers in Neuroscience, 13, 336. https://doi.org/10.3389/fnins.2019.00336 — review of the thermoregulation-sleep link in mammals: sleep onset and a fall in core temperature occur together, non-REM sleep is accompanied by core and brain cooling, and direct skin warming can shorten sleep latency; the authors propose that non-REM onset is most likely when core temperature is at its steepest rate of decline.
Okamoto-Mizuno, K., & Mizuno, K. (2012). Effects of thermal environment on sleep and circadian rhythm. Journal of Physiological Anthropology, 31, 14. https://doi.org/10.1186/1880-6805-31-14 — review of laboratory studies: with bedding and clothing in use, heat exposure increases wakefulness and reduces slow-wave and REM sleep, humid heat adds to the load, and cold exposure does not change sleep stages, though it does alter cardiac autonomic activity during sleep.
Minor, K., Bjerre-Nielsen, A., Jonasdottir, S. S., Lehmann, S., & Obradovich, N. (2022). Rising temperatures erode human sleep globally. One Earth, 5(5), 534–549. https://doi.org/10.1016/j.oneear.2022.04.008 — 7 million wristband sleep records from 47,628 adults in 68 countries matched to local weather; sleep shortened as nighttime minimum temperatures rose, steeply above 10°C, by about 14 minutes on nights above 30°C, mainly through later sleep onset. Larger effects in older adults, women, lower-income countries, and already-hot regions, with no evidence of adaptation. Measures outdoor temperature, not bedroom temperature.
Baniassadi, A., Manor, B., Yu, W., Travison, T., & Lipsitz, L. (2023). Nighttime ambient temperature and sleep in community-dwelling older adults. Science of the Total Environment, 899, 165623. https://doi.org/10.1016/j.scitotenv.2023.165623 — longitudinal in-home study with bedroom sensors and wearable sleep monitors in older adults; sleep was most efficient and restful at 20 to 25°C, with a 5 to 10% drop in sleep efficiency as temperature rose from 25 to 30°C. Nonlinear associations and substantial between-person variation. Older adults only.
Kräuchi, K., Cajochen, C., Werth, E., & Wirz-Justice, A. (1999). Warm feet promote the rapid onset of sleep. Nature, 401(6748), 36–37. https://doi.org/10.1038/43366 — 18 healthy young men, 144 data points; the distal-to-proximal skin temperature gradient in the late evening (an index of heat loss through the hands and feet) was the strongest predictor of sleep-onset latency, ahead of subjective sleepiness, core body temperature, melatonin, and heart rate.
Haghayegh, S., Khoshnevis, S., Smolensky, M. H., Diller, K. R., & Castriotta, R. J. (2019). Before-bedtime passive body heating by warm shower or bath to improve sleep: A systematic review and meta-analysis. Sleep Medicine Reviews, 46, 124–135. https://doi.org/10.1016/j.smrv.2019.04.008 — 17 studies included, 13 in the meta-analysis; a warm shower or bath at 40 to 42.5°C improved self-rated sleep quality and sleep efficiency, and when taken one to two hours before bed for as little as 10 minutes, significantly shortened sleep-onset latency. The authors note the evidence base is small and optimal timing is not settled.
Ko, Y., & Lee, J.-Y. (2018). Effects of feet warming using bed socks on sleep quality and thermoregulatory responses in a cool environment. Journal of Physiological Anthropology, 37, 13. https://doi.org/10.1186/s40101-018-0172-z — six young men, randomized crossover, 7-hour sleep at 23°C with and without bed socks, actigraphy: sleep-onset latency 7.5 minutes shorter, total sleep time 32 minutes longer, fewer awakenings, sleep efficiency 7.6% higher with socks; foot skin temperature 1.3°C higher; no change in core temperature or subjective ratings. Very small sample, young men only.
Raymann, R. J. E. M., Swaab, D. F., & Van Someren, E. J. W. (2008). Skin deep: Enhanced sleep depth by cutaneous temperature manipulation. Brain, 131(2), 500–513. https://doi.org/10.1093/brain/awm315 — thermosuit study in young adults, healthy older adults, and older adults with insomnia; a 0.4°C rise in skin temperature with no change in core temperature reduced nighttime wakefulness and shifted sleep toward deeper stages, with the largest effect in older participants, whose probability of early-morning awakening fell from 0.58 to 0.04.
Lack, L. C., Gradisar, M., Van Someren, E. J. W., Wright, H. R., & Lushington, K. (2008). The relationship between insomnia and body temperatures. Sleep Medicine Reviews, 12(4), 307–317. https://doi.org/10.1016/j.smrv.2008.02.003 — review: sleep-onset insomnia is associated with a delayed core temperature rhythm, sleep-maintenance insomnia with elevated nighttime core temperature, and combined insomnia with a 24-hour elevation; the hypothesis that impaired heat loss from the hands and feet drives this has not been consistently supported.
Irish, L. A., Kline, C. E., Gunn, H. E., Buysse, D. J., & Hall, M. H. (2015). The role of sleep hygiene in promoting public health: A review of empirical evidence. Sleep Medicine Reviews, 22, 23–36. https://doi.org/10.1016/j.smrv.2014.10.001 — sleep-hygiene advice alone is a weak treatment for a clinical sleep disorder.
Edinger, J. D., Arnedt, J. T., Bertisch, S. M., et al. (2021). Behavioral and psychological treatments for chronic insomnia disorder in adults: An American Academy of Sleep Medicine clinical practice guideline. Journal of Clinical Sleep Medicine, 17(2), 255–262. https://doi.org/10.5664/jcsm.8986 — strong recommendation for multicomponent CBT-I in adults with chronic insomnia; suggests clinicians not use sleep hygiene as a single-component therapy.
Thurston, R. C., Chang, Y., Buysse, D. J., Hall, M. H., & Matthews, K. A. (2019). Hot flashes and awakenings among midlife women. Sleep, 42(9), zsz131. https://doi.org/10.1093/sleep/zsz131 — 168 peri- and postmenopausal women, sternal skin conductance to detect hot flashes objectively plus wrist actigraphy at home; wake coincided with 78% of objectively recorded nocturnal hot flashes, and the odds of being awake in the five minutes after a flash were over five times those in the ten minutes before it, whether or not the flash was reported.