Hot summer nights can make it harder to fall asleep—and stay asleep. If you’ve been waking up sweaty or lying awake long after bedtime, your bedroom temperature could be part of the problem.
Chitra Lal, MD, clinical professor of pulmonary, critical care, and sleep medicine and director of University of Utah Health’s Sleep Wake Center, has helped many patients overcome persistent sleeplessness by troubleshooting a common culprit: body temperature.
Small changes to your sleep environment, paired with simple lifestyle habits, can help you wind down and improve the quality of your rest.
Simple Habits to Help You Sleep Better
As bedtime approaches, your core body temperature naturally drops by 1–2°F. Setting your thermostat at 65–67°F can help support that process, although older adults may feel more comfortable slightly warmer—around 67–74°F.
A bedroom that is too warm can make it harder to get quality sleep by causing you to:
Take longer to fall asleep
Wake up more often during the night
Get less REM and slow‑wave (deep) sleep
Feel less rested in the morning
Your bedding matters, too. During the summer, choose breathable fabrics like cotton or linen fabrics. In colder months, switch to insulating fabrics like microfleece, but avoid using anything too warm that disrupts your body’s natural cooling process.
A cooler room works best when paired with healthy sleep habits. Lal also recommends these simple steps to help your body wind down each night:
Keep the room dark.
Skip caffeine within three to four hours of bedtime.
Avoid alcohol within four to six hours of bedtime.
Don’t watch TV or scroll on your phone in bed.
Go to bed only when you’re ready to sleep.
Clean your humidifier regularly if you use one.
Time Your Light Exposure
Temperature isn’t the only thing that affects your body’s internal clock. Light exposure also plays an important role in helping your body know when it’s time to sleep—and when it’s time to wake up.
It’s true that blue light disrupts sleep, but when timed correctly, it can actually help regulate your circadian rhythm. Here’s how to use it to your benefit:
Avoid blue light before bed
Put devices away at least a couple of hours before bed or switch them to ambient/night mode. Research has shown that evening blue light:
Delays sleep
Pushes your internal clock later
Makes it harder for your core temperature to drop
Use blue light in the morning
Early morning blue light can shift your circadian rhythm earlier and strengthen your natural wake‑up signal. You can find blue‑light therapy lamps at most major retail stores including pharmacies, department stores, and online shops.
Many people think improving insomnia relies only on relaxing before bed or going to sleep earlier. However, family medicine physician Dr. Chan Yan-mei cites research showing that daytime light exposure is actually the key to regulating sleep. If people chronically lack natural light, their circadian rhythms can easily become disrupted, making it difficult to sleep well even if they go to bed early. Research shows that camping and moderate sun exposure help adjust sleep cycles – a simple, free sleep aid.
The Day-Night Hormonal Handover Mechanism
Chan explains that while most people think of melatonin for sleep, there is also cortisol, commonly known as the "stress hormone." She describes cortisol as the body's "day-shift doctor." It surges to its daily peak 30-45 minutes after waking, then slowly declines throughout the day, reaching its lowest point late at night. Melatonin is the opposite – the body's "night-shift doctor." It stays very low during the day, starts rising around 9 PM, and peaks between 2-4 AM.
Chan states that when this day-night hormonal handover goes smoothly, the body naturally produces sleepiness. If this rhythm is disrupted, you may toss and turn even when it's time to sleep. Therefore, insomnia is often not just a night-time problem but the result of a full-day circadian rhythm imbalance.
Office Workers with Windows Have Better Sleep Quality
In modern lifestyles, many office workers spend all day indoors, assuming the bright environment is sufficient. However, indoor light levels differ vastly from outdoor natural light. Typical office lighting is about 300-500 lux – roughly 0.5% of a sunny day's 50,000-100,000 lux. Many people think they work in a "bright place," but their body's internal clock isn't receiving strong enough light signals.
Chan cites a 2014 study from the University of Illinois and Northwestern University published in the Journal of Clinical Sleep Medicine. The controlled study of 49 office workers showed that those in offices with windows had significantly longer sleep duration and better overall sleep quality, while the windowless group showed the opposite.
Chan explains that the body's circadian rhythm needs light to calibrate. If daytime light exposure is insufficient, the brain may not correctly distinguish day from night, affecting melatonin secretion and sleep quality.
A 30-Minute Walk Outdoors: Natural Light Regulates Sleep
So how can office workers improve their sleep? Chan further cites a 2013 study from the University of Colorado published in Current Biology. In this experiment, participants went mountain camping for one week, exposed only to natural daylight during the day and no artificial light at night. After just one week, participants' "desired sleep time" shifted a full 2 hours earlier. Someone who normally felt sleepy at 11 PM began yawning at 9 PM. In 2017, the research team followed up on a more practical question: most people can't take a week off to camp. They found that even camping only during weekends (Saturday and Sunday) achieved 69% of the effect of a full week of camping.
Chan notes that for office workers, this means avoiding sleeping in and scrolling on your phone on weekend mornings. Instead, stepping outside for a 30-minute walk can shift your entire week's "desired sleep time" earlier. You don't truly need to camp – a "mini version" of the method yields most of the benefits.
Many think improving insomnia requires medication or supplements, but morning light exposure has been proven to enhance sleep quality. Chan cites a 2016 systematic review from the University of Amsterdam. The review analysed 53 studies with 1,154 participants and found that morning light therapy helps shorten the time to fall asleep and improves insomnia. The stronger the light intensity, the more pronounced the effect.
Additionally, a 2022 double-blind study from Inha University in Korea, published in Psychosomatic Medicine, experimented on 56 post-stroke insomnia patients. Using a 10,000 lux light therapy lamp for 30 minutes each morning for just 2 weeks significantly shortened their sleep onset latency and improved sleep efficiency.
Simple Anti-Insomnia Habit: Open the Curtains When You Wake Up
Chan also shares that she personally struggled with insomnia as a resident physician. Now, the first thing she does upon waking every day is open the curtains to let natural light in, helping her body quickly start up its circadian clock. She suggests that if you chronically have sleep problems, try starting with 10-30 minutes of morning sunlight. It might bring unexpected improvements to your sleep.
Chan reminds that many people habitually sleep in until noon on weekends to catch up on rest, but this can further disrupt the circadian rhythm. She points out that rather than blindly extending sleep time, it's better to maintain a regular schedule and increase daytime sunlight exposure. Ideally, receiving natural light exposure daily is the simplest and most practical way to adjust your sleep cycle.
Winter insomnia affects sleep quality during colder months.
Causes include reduced daylight and stress from the holiday season.
Bright light exposure and light therapy can help manage symptoms.
It's normal to feel sluggishduring the winter. Cold temperatures and fewer hours of sunlight can mean less time outdoors and more time staring at our screens.
For some people, these cold-weather habits may contribute to a sleep disruption, known as winter insomnia. This isn't a clinical condition, but it might begin or worsen during the winter months.
"Although disturbances can vary, people commonly experience an increase in middle-of-the-night awakenings, waking up earlier than intended, difficulty falling asleep, or restless sleep," Dr.Nicole Moshfegh, PsyD, clinical psychologist and director of We Rise Psychology, Inc., told Business Insider. She explained that winter insomnia can be caused by achange in your moodor energy level, which affects your ability to unwind before bed or calm your mind when you wake up during the night.
Below, we talked to sleep experts about the signs of winter insomnia, what makes it worse, and what you can do if it's affecting your ability to get a good night's rest.
Filmstax/Getty Images
Are you experiencing winter insomnia?
Most adults need seven to nine hours of sleep for optimal health. But it's easy to overlook the quality of your sleep or how long it takes for you to fall asleep.
"People who experience winter insomnia have trouble falling and staying asleep, or getting restful sleep during the winter months," Dr. Raj Dasgupta, chief medical advisor for Sleepopolis, told Business Insider. "They usually notice more night-time awakenings, lighter sleep, or a shift in their sleep timing."
He explained that winter insomnia is not a formal diagnosis. Instead, it's "a seasonal pattern of insomnia symptoms most likely from changes in light exposure, routine, and behaviour during winter," he added.
Dr. Jade Wu, a board-certified sleep psychologist and Mattress Firm sleep advisor, agreed, saying there are no clinical signs to differentiate winter insomnia from other types of insomnia you might experience throughout the year.
"In some ways, it's easier to have insomnia in the summer due to the longer daylight late into the evening hours, which stimulates our circadian alerting signals," she said. These signals tell us when to wake up and be alert.
"But in winter, people are more likely to be sedentary and not have enough light exposure, so this can make them more vulnerable to insomnia and circadian problems," she said. Another factor contributing to poor sleep is our eating habits, such as reaching for certain foods out of comfort or convenience.
Causes of winter insomnia
"With reduced daylight, we have less outside signalling for our brains to know when it's day versus night, which can cause our circadian rhythms to become less strong or stable," Wu explained. "A less stable circadian rhythm can disrupt sleep quality."
Some people try to compensate for the lack of sunlight by relying on bright indoor lighting, which leads to greater alertness in the evening and difficulty falling asleep. "Over time, these shifts can disrupt the circadian rhythm and make sleep timing feel less predictable," Moshfegh said.
Less exposure to natural light, especially in the morning, may also contribute to seasonal mood changes, such as anxiety, depression, or seasonal affective disorder (SAD), Dasgupta noted. Signs of SAD include feeling depressed or being unable to find pleasure in previously enjoyable activities.
"Depression includes many physical symptoms like fatigue, sluggishness, and changes in appetite and sleep," Wu said. You may also notice mental symptoms, such as reduced motivation or difficulty concentrating.
"Because sleep and mood have a bidirectional relationship, the lower our mood, the more we experience sleep disturbances and vice versa," Moshfegh said. Both she and Dasgupta emphasized that the stress of the holiday season, combined with irregular schedules, increased alcohol use, and cold and flu season, can get in the way of healthy habits like exercising or cutting down on takeout orders.
"Many people experience increased loneliness, family challenges, grief, and pressure around goals and self-improvement during this time of year," Moshfegh said. "These experiences can all cause and contribute to stress, which is one of the most potent disruptors of sleep."
How to cope with winter insomnia
There are several ways to minimize sleep disruptions. "The most powerful tool we have is bright light exposure, which means being outdoors and being near brighter windows when you have to be indoors," Wu said.
If clouds are in the forecast or you work in low-light conditions, one option is to use a bright light therapy light box. "Make sure to check with your doctor before using a light box, because it can cause significant problems for some people," she said.
Some of these behaviours might feel good, but restful sleep is more important
A good night's sleep is the absolute best form of self-care. But several common night time behaviours may be wrecking your ability to fall asleep, stay asleep, and consistently get quality rest. Each habit impacts people differently, and some might unexpectedly help you stay asleep. (If you swear scrolling your phone helps you sleep better, don't stress over it.) However, if you’re struggling with a bout of poor sleep, start by eliminating every sleep habit on this list that applies, then add them back one-by-one to find the culprit. We spoke with sleep experts about the worst sleeping habits and how to get back on track.
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Phone Usage
Several experts agree that it’s a good idea to limit your phone use before bed. “Most people are on their phones or watching late at night, which suppresses melatonin,” sleep expert Olivia Arezzolo explains. This can make it hard for people to fall and stay asleep.
Andrea López-Yianilos, PsyD, says to power down all devices and do something else at least an hour before bed. If you have to be on your phone, you could try blue light blocking glasses or the "Night Shift" (on iPhone), which warms the colours on the display. These steps could reduce the impact of blue light, although studies are inconclusive.
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Eating or Drinking
Eating or drinking within three hours before bed can make for a restless night. And there’s one beverage (the nightcap) that seems like it helps when it actually doesn’t.
That glass of wine might make you feel drowsy, but if you drink it right before bed, it could mess with your sleep quality by disrupting REM sleep. "When alcohol metabolizes, you get dehydrated," López-Yianilos explains, "So you'll have more fitful sleep."
When it comes to eating, moderation is key. Too much or too little food before bed could impact your sleep quality. Try to schedule meals at least three hours before bedtime, and if you get hungry late at night, stick to a small yet filling snack, like nut butter on crackers, López-Yianilos suggests.
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Exercising
Avoid working out too close to bedtime because exercise raises your body temperature, López-Yianilos explains, and your body temperature should naturally dip as you get ready to sleep.
However, this doesn’t mean never exercising. Just 30 minutes of moderate-intensity aerobic activity during the day can help you sleep better.
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Not Winding Down
This bad sleep habit is more about not having a habit at all. We should all set aside some time before bed to wind down. “If you are working, scrolling, cleaning, and planning until the second you get into bed, you can expect to have a hard time falling asleep,” says sleep coach Teresa Power.
“Like children, adults need both time and routine to prepare for rejuvenating, healthy sleep. Keep in mind, you don't need a 10-step, two-hour bedtime routine, but you do need to give your mind and body time to wind down and relax before sleep.”
Teresa Power recommends setting an alarm at least an hour before you plan to be in bed to finish up the show you're watching, make sure the lights are dim, put your phone aside, start washing up, and do whatever you have time to do to relax yourself.
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Overthinking
Overthinking (or ruminating) can be a bad habit that is hard to break, but there are several ways to get this under control. For starters, return to your breath. “Breathwork helps distract from your racing thoughts and calm your nervous system to relax your back to sleep,” says Power.
“Nasal breathing specifically increases production and release of nitric oxide, which helps blood, nutrients, and oxygen travel throughout your body. My favourite breathwork exercises are very simple; try box breathing or the 4-7-8 method.”
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Staying in Bed
One bad sleep habit people make when they can't fall asleep is staying in bed too long. Here’s what you should do instead, according to Arezzolo:
If you are awake longer than 20 minutes, get out of bed.
Go into the lounge and put on blue light blocking glasses if you have them. If not, just keep lights down low and avoid devices like the TV or phones.
Read, meditate or listen to calming music.
Only return to bed when you are just about to fall asleep.
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Ambient Light
Some people have sheer curtains and have no trouble falling or staying asleep. But if you're struggling with poor sleep quality, consider the ambient lighting in your sleep environment, which can cause all sorts of sleep disturbances. These sources can revolve around other night time habits, like playing video games without fully unplugging the console afterward.
If you live in a city with streetlights or have electronics in your room, light pollution and ambient light exposure might be what is hindering your sleep. To fully darken a room, unplug TVs or devices with lighted panels and install some blackout curtains or blackout roller shades. If there are some lights you can't turn off or block, try a comfortable sleep mask.
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Inconsistent Sleep Duration
“One mistake I see is inconsistent sleep durations,” explains sleep specialist Nicole Shallow, M.Ed, BCBA. According to Shallow, you might try sleeping longer some nights to “catch up,” but when you do this, you may see a dip in total sleep, causing night wakings or early wakings.
Even if you have sleep debt, “the goal is to have [your] average sleep be more consistent every day, with consistent wake-up times, give or take an hour,” says Shallow.
If you are struggling with inconsistent sleep, commit to the same wake-up time all seven days of the week—yes, even over the weekend! "Your bedtime will shift to where it needs to be," López-Yianilos says.
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Sleep Dependency
Sometimes, we don’t even realize that we depend on something to get to bed. “A common thing I see and experience myself is sleep dependency challenges,” says Shallow. When you always have something, and suddenly it’s not there, it may hinder your sleep quality.
To address this, Shallow says to notice if anything has changed in the environment from when you fell asleep. “For example, if you fell asleep with a show on, notice if turning that same show on helps you fall back to sleep. In the short term, turning it on could be helpful until you develop a new routine and healthy sleep dependencies.”
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Sleeping Too Much or Too Little
For Arezzolo, who helps people find their sleep type, another major problem is being uncertain of how many hours of sleep you need. "Some people need 9, others only 7, others 8. The hours are largely dictated by your sleep type (chronotype), which is why it’s so important to know."
Sleeping outside your optimal range can set you up for lower sleep quality and worse brain function. In fact, getting 16 minutes less sleep than you need could result in cognitive interference—or more distractions—the next day.
For reference, Arezzolo says in her book Bear, Lion or Wolf that bears need 9 hours, lions need 7 hours, and wolves need 8 hours. These sleep types also describe when you have the most energy and what times you naturally go to sleep and wake up.
Bears have a standard schedule. They are most productive midday, slump in the early afternoon, and like to wind down in the evening.
Lions are early birds, and they have the most energy in the morning, so they like to go to bed early.
Wolves are the typical night owl, liking to stay up late and sleep in late. They are the most productive in the evening.
Continuous sleepis a modernhabit, not an evolutionary constant, which helps explain why many of us still wake at 3am and wonder if something’s wrong. It might help to know that this is a deeply human experience.
For most of human history, a continuous eight-hour snooze was not the norm. Instead, people commonly slept in two shifts each night, often called a “first sleep” and “second sleep.”
Each of these sleeps lasted several hours, separated by a gap of wakefulness for an hour or more in the middle of the night. Historical records from Europe, Africa, Asia and beyond describe how, after nightfall,familieswould go to bed early, then wake around midnight for a while before returning to sleep until dawn.
Breaking the night into two parts probably changed how time felt. The quiet interval gave nights a clear middle, which can make long winter evenings feel less continuous and easier to manage.
Artificial lighting is behind the drastic change in human sleep patterns (Getty/iStock)
The midnight interval was not dead time; it was noticed time, which shapes how long nights are experienced. Some people would get up to tend to chores like stirring the fire or checking on animals. Others stayed in bed to pray or contemplate dreams they’d just had. Letters and diaries from pre-industrial times mention people using the quiet hours to read, write or even socialise quietly with family or neighbours. Many couples took advantage of this midnight wakefulness for intimacy.
Literature from as far back as ancient Greek poet Homer and Roman poet Virgil contains references to an “hour which terminates the first sleep,” indicating how commonplace the two-shift night was.
How we lost the ‘second sleep’
The disappearance of the second sleep happened over the past two centuries due to profound societal changes. Artificial lighting is one of them. In the 1700s and 1800s, first oil lamps, then gas lighting, and eventually electric light, began turning night into more usable waking time. Instead of going to bed shortly after sunset, people started staying up later into the evening under lamplight.
Biologically, bright light at night also shifted our internal clocks (our circadian rhythm) and made our bodies less inclined to wake after a few hours of sleep. Light timing matters. Ordinary “room” light before bedtime suppresses and delays melatonin, which pushes the onset of sleep later.
The Industrial Revolution transformed not just how people worked but how they slept. Factory schedules encouraged a single block of rest. By the early 20th century, the idea of eight uninterrupted hours had replaced the centuries-old rhythm of two sleeps.
In multi-week sleep studies that simulate long winter nights in darkness and remove clocks or evening light, people in lab studies often end up adopting two sleeps with a calm waking interval. A 2017 study of a Madagascan agricultural community without electricity found people still mostly slept in two segments, rising at about midnight.
Long, dark winters
Light sets our internal clock and influences how fast we feel time passing. When those cues fade, as in winter or under artificial lighting, we drift.
In winter, later and weaker morning light makes circadian alignment harder. Morning light is particularly important for regulating circadian rhythms because it contains a higher amount of blue light, which is the most effective wavelength for stimulating the body’s production of cortisol and suppressing melatonin.
In time-isolation labs and cave studies, people have lived for weeks without natural light or clocks, or even lived in constant darkness. Many people in these studies miscounted the passing of days, showing how easily time slips without light cues.
Similar distortions occur in the polar winter, where the absence of sunrise and sunset can make time feel suspended. People native to high latitudes, and long-term residents with stable routines, often cope better with polar light cycles than short-term visitors, but this varies by population and context. Residents adapt better when their community shares a regular daily schedule, for instance. And a 1993 study of Icelandic populations and their descendants who emigrated to Canada found these people showed unusually low winter seasonal affective disorder (SAD) rates. The study suggested genetics may help this population cope with the long Arctic winter.
Research from the Environmental Temporal Cognition Lab at Keele University, where I am the director, shows how strong this link between light, mood and time perception is. In 360-degree virtual reality, we matched UK and Sweden scenes for setting, light level cues, and time of day. Participants viewed six clips of about two minutes. They judged the two minute intervals as lasting longer in evening or low-light scenes compared with daytime or brighter scenes. The effect was strongest in those participants who reported low mood.
A new perspective on insomnia
Sleep clinicians note that brief awakenings are normal, often appearing at stage transitions, including near REM sleep, which is associated with vivid dreaming. What matters is how we respond.
The brain’s sense of duration is elastic: anxiety, boredom, or low light tend to make time stretch, while engagement and calm can compress it. Without that interval where you got up and did something or chatted with your partner, waking at 3am often makes time feel slow. In this context, attention focuses on time and the minutes that pass may seem longer.
Cognitive behavioural therapy for insomnia (CBT-I) advises people to leave bed after about 20 minutes awake, do a quiet activity in dim light such as reading, then return when sleepy.
Sleep experts also suggest covering the clock and letting go of time measurement when you’re struggling to sleep. A calm acceptance of wakefulness, paired with an understanding of how our minds perceive time, may be the surest way to rest again.
