With beads of perspiration dotting your forehead, you check the weather conditions on your smartphone, and gasp at it — it’s a sweltering 90 degrees Fahrenheit out there! Unfortunately, nights in the summer months are only going to get hotter across America. It’s no wonder then that many of us ask the same question, "What's the best AC temperature for sleeping?"
The good news is, the human body already has a natural "smart thermostat" that self-regulates our core temperature to prime us for sleep. The bad news? Our inborn thermostat is extremely sensitive. When the external environment is off by just a few degrees, it’s enough to throw off your body’s internal thermostat. As a result, you find it that much harder to doze off, much less stay asleep till morning.
So, what AC setting should you choose to promote naturalistic, healthy sleep? If your home doesn’t have an AC unit or you prefer to reduce your energy bills, are there alternative ways to improve indoor airflow for a cooler temperature?
To answer all your pressing questions, we’ll dive deep into the scientific literature to reveal the best AC temperature for sleeping — and what you can do if you want to skip the air conditioning.
Please note: This article is meant for informational purposes only and is not intended as medical advice.
Your body has a built-in "smart thermostat" to optimize your sleep-wake cycle. But to make sure it actually works for your sleep schedule rather than against it, you need to support it with the right temperature range in your environment. This gives your body's thermoregulation system sufficient scope to fluctuate throughout the night as part of the regular workings of your circadian rhythm (the internal body clock).
To prepare your body for sleep, your circadian rhythm sets several biological processes in motion. One of which is the subtle variations in your core body temperature (CBT) over a roughly 24-hour period. These temporal changes of your core temperature help you meet your sleep need (the genetically predetermined amount of sleep your body needs).
During the day, your body temperature hovers around 98.6 degrees Fahrenheit (37 degrees Celsius) and is at its zenith around 6 p.m. When night falls, your CBT starts to decline, dipping to its lowest at roughly 4 a.m.
Scientists suggest that this heat release helps us doze off more easily. Running a bit cooler — up to 3 degrees Fahrenheit, to be exact — may also be your body's natural prompt for energy conservation while you snooze.
The subtle rise and fall of your core temperature is tied to your sleep-wake cycle, specifically your body's melatonin production. For the uninitiated, melatonin is a sleep-promoting hormone that's naturally produced under dim light conditions.
The setting of the sun, coupled with deliberate avoidance of artificial lighting, tells your body to begin secreting melatonin. This is known as dim light melatonin onset (DLMO) and occurs two to three hours before sleep. In the RISE app, DLMO marks the start of your Melatonin Window. This is the window of time when your body produces the highest levels of melatonin it will all night, making it the best time to go to bed.
So, how does melatonin production correlate with your body's thermoregulation? Scientific evidence indicates that the start and subsequent rise of melatonin secretion is "temporally coupled with" the decline in your body's temperature. At least 40% of your CBT's fluctuations can be credited to melatonin. This two-pronged phenomenon of melatonin peak and temperature dip initiates sleep so that you're inclined to doze off when night falls.
Your body's temperature regulation doesn't just set sleep in motion. It also keeps you asleep until the sun rises, relative to sleep homeostasis.
Sleep homeostasis is characterized by a daytime buildup and nighttime depletion of the drowsiness-inducing compound adenosine. You can think of the sleep homeostat as a seesaw in your brain that wants to be level. With every waking moment, adenosine accumulates in your brain so that the seesaw tilts toward one end. In an effort to rebalance the sleep homeostat, you gravitate toward sleep when night falls, so that your brain can purge itself of adenosine, relieving sleep pressure and balancing the seesaw.
However, sleep pressure doesn't steadily decline throughout the night. Instead, the bulk of sleep pressure (represented by slow-wave activity, one of the deeper stages of sleep) dissipates in the first half of nighttime sleep. This leaves you with little to no sleep pressure in the second half of the night. The stakes of you awakening before your alarm rings just got a lot higher.
To help you stay asleep and meet your sleep need, your body's internal thermostat is hard at work. If you recall, your CBT drops to its lowest point in the middle of the night (around 4 a.m.), just when your brain has probably let off most of the sleep pressure. This biological change safeguards your sleep until your CBT rises again in the early morning as a prelude to your cortisol awakening response (more on that later).
By now, you might’ve realized that cooler temperatures are often the most comfortable temperatures for sleep. In fact, sleep scientist Matthew Walker labels the thermal environment as “perhaps the most under-appreciated factor determining the ease with which you will fall asleep tonight, and the quality of sleep you will obtain.”
Here's more proof that your bedroom temperature greatly influences your sleep patterns:
As you can see, ample evidence points toward a cool room to mimic and support the natural dip in your body temperature for better sleep tonight. Because the definition of "cool" can be subjective, science recommends the best AC temperature for sleeping lies between 65 and 68 degrees Fahrenheit.
With that said, you won't want your bedroom to be too cold, say, below 55 degrees Fahrenheit. A too-cool sleep environment will only dampen your body's cortisol awakening response (CAR). This biological process takes place in the early morning hours when your body manufactures peak levels of cortisol. Because cortisol is an alertness-boosting hormone, CAR helps transition you from sleep to wakefulness.
However, cortisol is ultra-sensitive to heat — a mere 1-degree rise in your body's temperature is enough to trigger its secretion. But if your room is too chilly in the morning, your body won't be warm enough to produce sufficient cortisol and propel you into consciousness. As a result, you're more inclined to lounge in bed than get a head-start on the day or feel groggier than usual when your alarm forces you out of bed.
You now know the best AC temperature for sleeping. But what if you want to save money? Are there any energy-efficient ways to generate cool air without air conditioning?
It so happens that the best room temperature for sleeping doesn't necessarily have to rely on an AC unit. In fact, you can take advantage of the distal-to-proximal skin temperature gradient (DPG) to maintain the ideal sleeping temperature that won't compromise your comfort levels nor burden you with high energy costs.
DPG may sound complex, but it simply refers to how quickly heat is lost from various parts of your body. To calculate DPG, researchers subtract the temperature of distal sites (like your hands and feet) from the temperature of proximal sites, say, the head and stomach.
According to a 2014 study in the Journal of Biological Rhythms, "The change in DPG is reported to be a better predictor for sleep onset latency (SOL) than is melatonin onset, subjective sleepiness rating, or rate of CBT decline." A narrower DPG is favored, in which the "distal skin temperature warms and becomes closer to proximal skin temperature."
You can perfect a narrow DPG in real life without breaking out complex mathematical equations. It's all about distal vasodilation, in which blood flows more efficiently to your extremities. This intensifies heat loss through your hands and feet, bringing about a quicker drop in your core temperature.
Below, you'll learn five sleep tips on how to make distal vasodilation work for you. The beauty of these techniques is that they can be paired with or without an air conditioner so long as you reach the ideal sleeping temperature in the end.
It may sound counterintuitive to wear socks to bed. But people with chronically cold feet are scientifically proven to take longer to fall asleep.
That's where a pair of socks come in handy to promote distal vasodilation. Keeping your feet warm encourages blood to flow toward your soles. As we've mentioned, this aids the natural drop in your CBT to promote sleep.
In fact, one study shared that soaking your feet in warm water for 20 minutes before sleep "relieves fatigue and insomnia." You can easily replicate these benefits with the uncomplicated alternative of socks.
Note: If you have poor circulation issues, it's best to consult a healthcare professional on whether you should wear socks to bed or not.
If your room is too warm for socks, avoid covering up your entire body with your duvet. Leaving one or both feet exposed to the surrounding air can help facilitate the cooling process. To keep the room even cooler, a ceiling fan (or any type of fan device) efficiently circulates the airflow in the room for a more comfortable temperature.
Dive deeper: are there benefits to sleeping naked?
From nightwear to bedding to mattresses, the right fabrics play a key role in maintaining the best temperature for sleeping.
Go for natural or plant-based fabrics, such as cotton, linen, and silk, that are breathable enough to regulate your body temperature during sleep. The thickness of your nightwear and bedding also matters with the seasons. Thinner, lighter materials are recommended for the warmer months, while thicker, heavier bedclothes and covers will keep you warm during the cooler seasons.
If you identify as a hot sleeper (you tend to overheat during sleep), invest in a cooling pillow and/or a gel-infused memory foam mattress. These simple adjustments can help maintain your body temperature, so you’re less likely to break out into a night sweat.
A warm bath or shower is another effortless way to support and quicken the natural drop in your CBT prior to sleep.
Warm water dilates your skin's superficial blood vessels. Stepping out of the bathroom exposes the dilated vessels to the relatively cool air, prompting a quick shift from hot to cold after your bath. What’s more, science shows that the temperature differential heightens your deep non-rapid eye movement (NREM) sleep by 10-15%.
Slotting in a warm bath or shower in the 1-2 hours before your target bedtime lessens the time taken to fall asleep. This makes it one of the perfect wind-down activities in the evening.
You may think that exercise before bed can help work off your nervous energy to help you sleep better at night. While it's true that morning and afternoon workouts benefit nighttime sleep, the same can't be said for physical training right before bed.
That's because any exercise of the moderate to vigorous variety hikes up your core temperature. Instead of signaling to your body it's time for bed, your higher-than-usual temperature only intensifies your wakefulness. Because you take longer to cool down, you're now more likely to stay up past your target bedtime.
To make exercise work for your nighttime sleep rather than against it, check out our guide on the best times for working out.
Your ambient temperature is only one piece of the puzzle to the perfect sleep environment — the other two missing pieces are complete darkness and silence.
The advantage of knowing about the ideal sleep environmental conditions is that once you've locked into your sweet spot (read: cool, dark, and quiet), you can set them by default without having to pay too much attention to them. So, things like investing in a programmable thermostat, putting up blackout curtains, and soundproofing your room will pay off in the long run, as they help you meet your sleep need every night.
But the optimal sleep environment is just the tip of the iceberg when it comes to good sleep hygiene. Ideally, the upkeep of sleep-promoting behaviors for naturalistic, healthy sleep should take place 24/7. What you do during daylight directly impacts your sleep that night.
To learn about how to perfect your sleep hygiene, bookmark our step-by-step Sleep Guide.
As you can see, the best AC temperature for sleeping is reminiscent of your childhood Goldilocks tale — not too hot, not too cold, but just right. In which case, apply the golden rule of 65-68 degrees F.
Even if your room isn't air conditioned, there are various hacks you can try to activate and maintain the ideal sleep temperature throughout the night. Simple tweaks to your daily routine, like taking a warm bath or shower before bed, help mimic and support your body's natural temperature drop. This way, you’re apt to fall asleep more quickly and stay asleep throughout the night.
Still, the best AC temperature for sleeping is only a subset of healthy sleep hygiene. That's why we created the RISE app that tells you when to do the right sleep-for-energy-promoting activities according to your unique chronobiology. Because when you sleep better at night, you're armed with better energy during the day to do the things you desire.
RISE makes it easy to improve your sleep and daily energy to reach your potential
RISE makes it easy to improve your sleep and daily energy to reach your potential
