Improving Summer Sleep Comfortably in Japan! Tips for Increasing Sleep Duration

English version

Have you ever struggled to fall asleep during summer nights due to heat and humidity? Many people face the challenge of sweaty sheets or rooms without effective air conditioning, turning their bedrooms into sauna-like environments. Dealing with daytime heat can drain your energy, making it difficult to get restful sleep at night, which in turn affects your overall health and performance the next day. Particularly during ‘tropical nights’ where nighttime temperatures stay above 25 degrees Celsius, sleep quality significantly decreases.

Quality sleep is crucial for maintaining good health, but achieving it in summer can be challenging. This article provides specific strategies for sleeping soundly on summer nights and tips for creating a comfortable sleep environment. From using air conditioning effectively to choosing the right bedding and managing daytime activities, we approach the topic from various angles. Discover tips to ensure a comfortable summer night’s sleep that beats the heat.

The causes of decreased sleep quality

The reasons for decreased sleep quality on summer nights are diverse. Below, I will explain in detail the main factors contributing to this.

1. Hot and humid climate

In summer nights, temperatures are high and humidity rises. The human body enters deep sleep by lowering its temperature during sleep, but higher temperatures hinder this temperature regulation, making it difficult to fall asleep. Additionally, high humidity reduces sweat evaporation, increasing discomfort. This often leads to frequent awakenings and consequently, a decrease in sleep quality.

2. Impact of Tropical Nights

The term ‘tropical night’ refers to nights where the minimum temperature stays above 25 degrees Celsius. On such nights, the bedroom temperature remains high, making it difficult for the body to relax and enter deep sleep due to the lack of an appropriate temperature environment for rest. Even with air conditioning or fans, it can be uncomfortable if the room becomes too cold, complicating effective temperature regulation.

3. Rising Humidity

High humidity makes it difficult for sweat to evaporate, leading to a higher perceived body temperature than the actual air temperature. This causes sticky skin, increased discomfort, and frequent awakenings during sleep. Moreover, high humidity environments promote the growth of mold and dust mites, potentially triggering allergy symptoms. These factors further contribute to deteriorating sleep quality.

4. Disruption of Daily Rhythm

Summer often brings vacations and numerous events, making it easy for daily routines to become disrupted. Continued irregularities such as staying up late or having irregular lifestyles can disturb the body’s internal clock, leading to decreased sleep quality. Especially when daytime activity levels are low, it can be difficult to feel sufficiently tired at night, which may result in difficulty falling asleep.

5. Impact of Light

During summer, days are longer and it becomes brighter early in the morning, making bedrooms more prone to light. This suppresses the secretion of melatonin, the sleep hormone, making it difficult to fall asleep. Particularly when direct sunlight enters the bedroom in the early morning, it can lead to waking up easily.

6. Psychological Factors

The heat of summer itself can become stressful, leading to prolonged states of discomfort that hinder relaxation and affect sleep quality. Additionally, the stress caused by frequent awakenings due to the heat can create a vicious cycle that further deteriorates sleep quality.

7. Impact of Diet

During summer, there are more opportunities to consume cold drinks and ice cream, which can sometimes strain the digestive system. Eating late at night can also slow digestion and contribute to difficulty falling asleep. Additionally, caffeine and alcohol can interfere with sleep.

These factors often intricately intertwine, causing decreased sleep quality on summer nights, which is a common concern for many people. In the next section, we will provide detailed explanations of specific strategies to address these issues.

Specific measures

To ensure comfortable sleep on summer nights, it is important to adjust your environment and lifestyle habits. Below are specific measures to achieve this.

1. Environmental adjustments

To create a comfortable sleep environment on summer nights, pay attention to the following points

●Temperature Control

The bedroom temperature directly affects comfortable sleep. If using air conditioning, set it around 25 degrees Celsius for optimal comfort. For those sensitive to air conditioning, using a fan to promote air circulation can be effective. Additionally, using cooling mats or gel pads can help lower perceived body temperature.

●Humidity Control

High humidity is a barrier to comfortable sleep. Use an air conditioner with dehumidifying function or appropriately use a humidifier to regulate humidity levels.

2. How to Choose Bedding

●Choosing Breathable Materials

Opt for bedding made from natural materials like cotton or linen. These materials absorb sweat well and offer good airflow, helping to reduce night sweats and support comfortable sleep. Cooling sheets and pillowcases with cooling effects can also be effective for managing heat.

●Cleanliness of Bedding

Especially during sweaty summer months, cleanliness of bedding is crucial. Regularly wash your bedding to maintain cleanliness. Additionally, review the replacement schedule of your bedding regularly to ensure they remain clean and fresh.

3. Preparing for Bed

●Temperature Regulation

Taking a shower before bed and lowering your body temperature can make it easier to fall asleep. Cooling your body with lukewarm water especially helps lower internal temperature and promotes easier onset of sleep.

●Relaxation Habits

Prioritize relaxing activities before bedtime. Listening to calming music or incorporating aromatherapy can help relax your mind and body, improving the quality of sleep.

4. Reviewing Lifestyle Habits

●Maintaining a Regular Lifestyle Rhythm

When your daily routine is disrupted, your body clock can become unsettled, leading to lower sleep quality. Especially in summer when daytime activities tend to be irregular, strive to wake up and go to bed at consistent times.

●Moderate Exercise

Moderate exercise helps to tire the body and facilitate deeper sleep. Incorporating light exercise, especially in the early morning or evening, can help your body relax more easily.

5. Psychological Relaxation

●Stress Management

The summer heat and irregularities in daily life can become sources of stress, potentially reducing sleep quality. It’s important to create a relaxing environment and reduce stress. Incorporate relaxation techniques such as mindfulness and deep breathing to refresh both your mind and body.

By implementing these measures, you can achieve comfortable sleep even during summer nights. Given that sleep quality tends to decline in the summer, actively maintaining a conducive environment and reviewing lifestyle habits can support healthy sleep.

Points for Reviewing Lifestyle Habits

Reviewing lifestyle habits is a crucial factor in improving sleep quality. Particularly in summer, changes in temperature, sunlight exposure, and activity levels can significantly impact sleep. Establishing a regular daily routine is key. Below, I will detail specific points for reviewing lifestyle habits.

1. Establishing a Regular Sleep Schedule

During the summer, with longer daylight hours affecting our circadian rhythms, establishing a regular sleep schedule helps align our internal clocks and promotes deep sleep. It’s important to cultivate habits of going to bed and waking up at the same time each day. Avoiding late nights and oversleeping, and maintaining a consistent rhythm, can improve the quality of sleep.

2. Aligning Circadian Rhythms

Summer vacations and heat often lead to a tendency for reversed day-night rhythms, but it’s important to maintain a routine of daytime activity and nighttime rest. Incorporating moderate exercise and outdoor activities during the day can help awaken the body and facilitate deeper sleep at night. Exposure to bright light also aids in regulating the circadian rhythm.

3. Managing Meals and Hydration

The content and timing of meals, as well as hydration intake, are crucial factors directly affecting sleep. In summer, appetite tends to decrease, leading to increased consumption of cold drinks and light snacks. However, consuming large amounts of food late at night can hinder digestion and lower sleep quality. It’s advisable to have a light dinner and moderate fluid intake before bedtime. Additionally, caffeine and alcohol can disrupt sleep, so it’s recommended to avoid consuming them at night.

4. Relaxation of Mind and Body

Stress and tension are significant factors that can lower the quality of sleep. Summer, with its heat and seasonal changes, often increases stress levels. It’s important to incorporate relaxation techniques such as deep breathing, meditation, and other relaxation methods into daily routines to refresh both mind and body. Particularly, prioritizing relaxation time before bed and creating an environment that reduces stress are crucial steps.

5. Creating a conducive sleep environment

Creating a comfortable sleep environment directly enhances the quality of sleep. Adjusting room temperature and humidity, selecting appropriate bedding, and preventing noise and light disturbance all contribute to promoting restful sleep. Especially during summer, using air conditioning or fans to maintain a comfortable room temperature and opting for breathable bedding are crucial.

By being mindful of these points and reassessing lifestyle habits, you can achieve healthy and restorative sleep even during summer nights. Improved sleep quality boosts daytime energy levels and lays the foundation for a healthier life.

Revising Lifestyle Habits for Healthy Summer Sleep

To ensure high-quality sleep during summer nights, it is essential to review your lifestyle habits. Establishing a regular sleep schedule, adjusting your day-night rhythm, managing diet and hydration appropriately, incorporating relaxation techniques for mind and body, and maintaining a comfortable sleep environment are key points. By practicing these measures, you can maintain stable and healthy sleep despite summer heat and stress. The refreshing effects of good sleep can positively impact overall daily life and support a healthy lifestyle.


The reasons for decreased sleep quality during summer nights include factors such as hot and humid weather, tropical nights, rising humidity levels, disrupted daily rhythms, light exposure, psychological factors, and dietary influences. These factors intertwine to often hinder comfortable sleep, posing a common concern for many people.

However, by implementing specific measures, it is possible to ensure high-quality sleep even during summer nights. First and foremost, it is crucial to manage room temperature and humidity, choose bedding with good ventilation, and optimize the sleep environment. Additionally, incorporating practices that regulate body temperature and promote relaxation can improve ease of falling asleep.

Furthermore, establishing a regular daily rhythm, engaging in moderate exercise, and managing stress through lifestyle adjustments are also crucial. Paying attention to the timing and content of meals and fluids, and prioritizing relaxation before bedtime, can facilitate mental and physical refreshment.

By practicing these strategies, one can overcome the challenges posed by summer heat and humidity, achieving healthy and comfortable sleep. Improved sleep quality enhances daytime activities and overall quality of life. For those struggling with sleep issues during summer, incorporating these strategies can support a healthier lifestyle.