You turned the heat on, and now you wake up at 3 a.m.

First cold night of the season. You turn the heat on and pull out the duvet and your flannel pyjamas. You fall asleep nice and cozy, then open your eyes at 3:10 a.m., sweaty and with a dry throat. What if your heating is what's waking you up at 3 a.m.? An overheated bedroom is one of the habits that secretly ruin your sleep, and it comes back every fall. The good news: a few simple adjustments are all it takes to find the best bedroom temperature for sleep.

Why does a bedroom that's too warm wake you up in the middle of the night?

To sleep well, your body temperature needs to drop slightly. In a room that's too warm, it stays too high. Your sleep becomes more restless and you wake up more often, especially in the second half of the night.

Your body needs to cool down to sleep

Your body temperature follows a 24-hour cycle. It starts to drop about two hours before bedtime, just as melatonin rises. It keeps going down during the night, reaching its lowest point in the early morning.

This thermoregulation happens mainly through your skin, hands and feet, which release your internal heat. A cool bedroom makes that job easier. A warm bedroom, on the other hand, slows it down. Your body holds on to its heat, falling asleep takes longer and deep sleep becomes harder to come by. The result: you're too hot at night without understanding why, even if you felt cold all evening.

Why 3 a.m.?

Waking up at 3 a.m. has a simple explanation. Early in the night, your sleep is deep and it's hard to wake you. Around the middle of the night, it gets lighter, and the slightest discomfort is enough to wake you up.

And by then, heat has been building up under the duvet for hours. The baseboard heaters have kept running, your flannel pyjamas are trapping sweat and your mattress has stored up your body heat.

Too much heat plus light sleep is often what wakes you up. The exact time depends on when you go to bed, so for you it might be 2:30 or 4 a.m. When you wake up, avoid checking the time on your phone. The screen light and counting the hours you have left make it harder to fall back asleep.

Dry air from the heating, the other culprit

Heating doesn't just raise the temperature. It also dries out the air. In winter, the outdoor air holds little moisture, and it gets even drier once it's warmed up inside the house.

Dry air in the bedroom in winter can cause a dry throat, a stuffy nose, chapped lips and irritated eyes. These small discomforts can also wake you up, especially toward morning. If you feel hot even in a cool room, the cause may be hormonal, like hot flashes at night.

What's the best bedroom temperature for sleep?

The ideal temperature for sleep is around 16 to 19 °C for most adults. The Quebec government recommends 17 °C at night in its energy efficiency brochure (in French). A cool bedroom helps your body cool down, as long as your bed is warm enough. Avoid lowering the temperature by more than 3 degrees at once, though, since the same brochure warns that too sharp a drop causes discomfort and humidity problems. If your home is at 21 or 22 °C, bring it down in stages.

Other benchmarks point the same way, and CAA-Quebec recommends lowering the temperature to between 18 and 19 °C at night, as in unused rooms. In the United States, the Sleep Foundation suggests about 18 °C. These numbers seem low when you live in a home kept at 21 or 22 °C.

But under the covers, your body doesn't feel the room temperature the same way. The best bedroom temperature for sleep also depends on your bedding, your pyjamas and how sensitive you are to cold.

Some people sleep very well at 16 °C, while others prefer 19 °C. The simplest approach is to adjust one degree at a time, then watch how you sleep for a few days before changing it again.

Baseboards, thermostat, heat pump: setting your bedroom heating right

Yes, it's better to turn down the bedroom heating at night. When you lower the thermostat by a few degrees, your body cools down more easily and your electricity bill goes down. The right method depends on your heating system, though, whether it's electric baseboards, a smart thermostat or a heat pump.

• Electric baseboards. Install a programmable electronic thermostat in your bedroom. More accurate than an old thermostat, it lowers the temperature on its own, at the time you choose.
• Programmable or smart thermostat. Set it to lower the temperature one hour before bedtime and raise it again 30 minutes before you wake up. You sleep cool and get up warm.
• Heat pump. Make sure the warm air isn't blowing directly onto your bed. If the heat pump is in another room and your bedroom gets too warm, keep the door closed. Many wall-mounted models also have a night mode that lowers the temperature automatically.

Duvet, pyjamas, mattress: the heat that comes from your bed

The classic fall trap is pulling out the winter duvet the same night you turn the heat on. You double the heat all at once and end up too hot at night. It's better to wait a few weeks and layer a sheet, a light blanket and a lighter all-season duvet that are easy to take off.

A wool or light down duvet also regulates heat better than a very thick synthetic one. As for pyjamas, cotton lets your skin breathe better than fleece or thick flannel.

A warm shower an hour or two before bed helps too. When you step out, blood flows toward your skin, which then speeds up heat loss from your body and makes it easier to fall asleep.

Your mattress also plays an important role. A very dense foam mattress can hold on to body heat all night. Polysleep mattresses, made in Quebec, use a ventilated hybrid foam designed to let air circulate better.

Keep an eye on humidity too. A humidifier can help if the air is very dry, aiming for a relative humidity between 30 and 40% in winter, to avoid condensation and mould on the windows during cold snaps. A small hygrometer lets you check the level at a glance. Clean your humidifier every week, since standing water encourages mould and bacteria.

Still waking up at 3 a.m.? The other suspects

Waking up at 3 a.m. on a regular basis isn't always about temperature. Stress, alcohol, caffeine, your phone and needing to pee can also interrupt your night. The best approach is to go through these suspects one by one, starting with the easiest to change.

• Your 3 p.m. coffee counts, because afternoon caffeine stays in your body for several hours and makes your sleep lighter.
• Screens play a role too, since checking your phone in bed delays falling asleep and its notifications trigger micro-awakenings.
• Alcohol is deceptive as well, because that evening glass of wine helps you fall asleep but breaks up the second half of the night.
• Changing bedtimes take a toll, and an irregular sleep schedule throws off your internal clock.
• Stress and racing thoughts can wake you up in the middle of the night, then keep you from falling back asleep.
• Needing to pee also interrupts the night, especially if you drink a lot in the evening.
• A heavy or spicy meal eaten late raises your body temperature during digestion, right when it should be cooling down.

To get a clearer picture, write down your bedtime, when you wake up during the night, your last cup of coffee and your bedroom temperature for one week. This little sleep diary often brings out the real culprit. If these wake-ups have been happening almost every night for several weeks, talk to a doctor. They can check for a medical cause and point you toward the right solution.

FAQ

Is it better to sleep with the window open a crack in winter?

It can help, but in moderation. A window open a crack cools the room and brings in fresh air, but it creates drafts and drives up your energy use in the middle of winter. The best compromise is often to air out your bedroom for 10 minutes before bed, then close the window for the night.

Why am I hot at night when my bedroom is cool?

There are several possible causes. Bedding that's too warm, a mattress that holds heat, a heavy meal or a drink in the evening can all raise your temperature. Hormonal changes also play a role for many people. Our article on night sweats offers more specific insight into these causes.

Does wearing socks to bed help you fall asleep faster?

Often, yes. Warm feet dilate your blood vessels and help your body release its internal heat faster, so you fall asleep more easily. It's the best of both worlds: a cool room for your body and warm extremities to help you drift off.

Does turning down the heat at night really save money?

Yes. When you turn down the heat at night, your home uses less energy. On top of that, according to the Quebec government's energy efficiency brochure, an accurate electronic thermostat can save up to 10% on heating costs. Together, these two habits give you a double benefit: better sleep and a lighter electricity bill.

Can a bedroom that's too cold also affect sleep?

Yes. When your hands and feet are cold, your body has a harder time releasing its internal heat, and falling asleep takes longer. The ideal temperature for sleep therefore combines a cool room and a comfortably warm bed, with socks and a few layers of bedding.

Conclusion

When the cold weather arrives, the right move isn't to turn the bedroom thermostat up, but down. A room around 17 °C, air that isn't too dry and layered bedding help your body cool down. That's often all it takes to find the best bedroom temperature for sleep and get through the night without waking up.

A cool bedroom, layered bedding and a ventilated foam mattress from the Polysleep collection are the winning trio for winter nights. Our mattresses are made in Quebec and designed to let air circulate, even when the heat is cranked up.