How to Sleep Better During Summer in Japan: Practical Tips for Hot and Humid Nights
My first summer in Japan was difficult for a reason I had not expected.
The heat itself was manageable, but the humidity was not. Even after sunset, the air felt heavy, the bedding felt slightly damp, and I often woke up in the middle of the night feeling tired and sticky.
At first, I tried to solve the problem by lowering the air-conditioner temperature. Over time, however, I realized that managing humidity was just as important as cooling the room.
After spending many summers in Japan, I now rely on a few simple habits that help me sleep more peacefully during hot and humid nights.
Why Is It Hard to Sleep During Summer in Japan?
Japan’s summer climate combines high temperatures with high humidity.
Before sleep, the body naturally releases heat and gradually lowers its core temperature. When the bedroom is warm and humid, sweat does not evaporate as easily, making it harder for the body to cool down.
This is why humid nights in Japan can feel exhausting even when the temperature does not seem unusually high.
Japan also has a term called nettaiya, or “tropical night.” It refers to a night when the temperature does not fall below 25°C, or 77°F.
During these nights, falling asleep can take longer, and waking up several times before morning is common.
Use the Air Conditioner Without Feeling Guilty
When I first moved to Japan, I often heard that leaving the air conditioner on overnight was unhealthy.
Because of that, I used the timer and expected the room to stay cool until morning.
It rarely worked.
A few hours after the unit switched off, the bedroom became warm again, and I woke up feeling uncomfortable. I eventually found that leaving the air conditioner on at a moderate setting gave me more restful sleep than repeatedly waking up in the heat.
There is no single ideal temperature for everyone. A setting that feels pleasant to one person may feel too cold to someone else.
The goal is to prevent the room from becoming overheated without making it uncomfortably cold.
Try pointing the airflow toward the ceiling or wall rather than directly at your face or body. A fan or air circulator can also distribute cool air more evenly around the room.
Try Dry Mode When the Room Feels Sticky
For several years, I ignored the Dry Mode button because I assumed regular cooling was always the better choice.
That turned out to be a mistake.
On humid nights in Japan, the room may feel unpleasant even when it is not especially hot. In that situation, reducing moisture can make a bigger difference than lowering the temperature.
Japanese air-conditioner remotes may label this setting as:
Dry
Dehumidify
除湿
ドライ
I now choose the mode according to how the bedroom feels.
If the room is hot, I use cooling mode. If it feels damp and sticky, Dry Mode often makes the air feel lighter and easier to sleep in.
Choose Breathable Summer Bedding
Japan has many bedding products designed for humid summers.
Cooling mattress pads and pillow covers are popular, but the material is just as important as the cooling label.
Cotton, linen, and gauze allow more airflow and are generally easier to wash during the hottest months.
During my first summer, I was surprised by how quickly my pillowcase started to feel damp. Washing every piece of bedding daily was unrealistic, so I began changing the pillowcase more often instead.
That small habit made the bed feel much fresher.
A washable cooling pad can also help, especially if the mattress itself retains heat.
When shopping for summer bedding, I recommend checking three things:
Breathability
Washing instructions
How the fabric feels against your skin
A product that feels cool in the store may not stay pleasant throughout the night if it does not release moisture well.
If you are also wondering why Japan’s summer air feels so heavy, read my guide to why summer in Japan feels so hot and humid.
Take a Lukewarm Shower Before Bed
A freezing shower may sound appealing after a hot day, but I find that a lukewarm shower helps me relax more effectively.
A very cold shower can feel refreshing for a few minutes, while a very hot bath may leave the body feeling warmer afterward.
A short lukewarm shower removes sweat without making me feel overly chilled or alert.
It is also important to drink enough water during the day. However, drinking a large amount immediately before bed may lead to repeated bathroom trips during the night.
I prefer to stay hydrated regularly and keep only a small glass of water near the bed.
Put Your Phone Away Before Bed
This is still one of the hardest habits for me.
I sometimes pick up my phone intending to check one thing, then realize that thirty minutes have passed.
On a humid night, scrolling can feel easier than trying to sleep, but it usually delays bedtime even further.
These days, I try to put my phone away about 30 minutes before bed.
I dim the lights, read a few pages of a book, or listen to something quiet instead. This helps create a clearer transition between the busy part of the evening and sleep.
Keeping roughly the same waking time each day also helps. Sleeping very late on weekends can make Sunday night much harder than it needs to be.
Fan or Air Conditioner: Which Is Better?
A fan can be enough on a mild night, especially if the room is already cool and the humidity is low.
However, a fan only moves the existing air. It does not lower the room temperature or remove moisture.
On very hot or humid nights, the air conditioner is usually more effective. You can also use both together, with the fan circulating cooled air around the room.
Avoid placing a strong fan directly beside your face for the entire night. Gentle airflow from a distance is usually more pleasant.
A Simple Summer Sleep Routine
You do not need an expensive collection of cooling products.
A basic routine can be enough:
Cool the bedroom before going to sleep.
Use Dry Mode if the room feels humid.
Keep air from blowing directly onto your body.
Choose light, washable bedding.
Take a lukewarm shower.
Put your phone away before bed.
Drink water regularly during the day.
Once I started focusing on humidity rather than temperature alone, I stopped waking as often during the night. I still use the same routine every summer.
Frequently Asked Questions
Is it safe to leave the air conditioner on overnight?
Many people find it easier to sleep when the air conditioner remains on at a moderate setting. Avoid extreme cooling and direct airflow, and choose a temperature that suits your body and room.
Is Dry Mode better than Cooling Mode?
Dry Mode is useful when the room feels humid but not extremely hot. Cooling Mode is usually more suitable when both the temperature and humidity are high.
Should I use a fan or an air conditioner?
A fan may be enough on a mild night. During very hot or humid weather, an air conditioner is more effective because it can cool the room and reduce moisture.
What bedding is best for summer in Japan?
Breathable, washable materials such as cotton, linen, and gauze work well. Cooling mattress pads and pillow covers can also help if they do not trap moisture.
What is nettaiya?
Nettaiya means a tropical night when the temperature remains at or above 25°C. These nights are common during Japan’s summer.
Final Thoughts
Sleeping during summer in Japan became much easier once I stopped trying to endure the heat and started adjusting the room properly.
The biggest improvement came from controlling both temperature and humidity.
A moderate air-conditioner setting, breathable bedding, a lukewarm shower, and less phone time before bed may sound like small changes, but together they can lead to more restful nights.
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