When temperatures rise, sleep often suffers. Hot nights can make it harder to fall asleep, increase waking during the night and leave people feeling less rested the next day.
One reason is thermoregulation, the body’s ability to keep its internal temperature within a safe range. Sleep is closely linked to body temperature: to fall asleep and stay asleep, the body usually needs to lose some heat. Hot bedrooms make that harder.
And UK summers are becoming hotter. The Met Office has reported that the chance of exceeding 40°C in the UK is now more than 20 times higher than it was in the 1960s, with a 50% chance of another 40°C day in the next 12 years.
Humidity can make the problem worse. Research on humidity and heat stress shows that high humidity can increase the strain heat places on the body. The body cools itself partly by sweating. As sweat evaporates from the skin, it carries heat away. But when the air is already humid, evaporation becomes less efficient.
So how can you sleep better in hot weather?
Air conditioning is one answer, but it is not affordable or practical for many households. According to the Energy Saving Trust, the electricity unit rate under the July to September 2026 price cap is 26.11p per kWh for direct debit customers. A small portable air-conditioning unit using about 1kW for seven hours a night over 30 nights would cost around £54.83 in electricity alone, before buying the unit.
Research on overheating in homes shows that shading and ventilation can be important passive cooling strategies: reducing indoor heat without mechanical cooling. Before cooling the air, then, it helps to reduce the heat entering the home. Overheating usually comes from sunlight entering through windows, known as solar gain, and warm outside air.
These eight steps can help keep bedrooms cooler before nightfall.
1. Keep sunlight out during the day
On sunny days, keep curtains or blinds closed on sun-facing windows. This reduces sunlight entering the room and heating up floors, walls and furniture. External shading, such as shutters, awnings or shades, can be even more effective because it stops some sunlight before it reaches the glass.
Be careful with windows. If the air outside is hotter than the air inside, opening windows can bring heat in. Open windows when the outside air is cooler than indoors, often early in the morning, evening or overnight. Close them during the hottest part of the day if the outside air is warmer.
2. Use cross-ventilation when the air outside is cooler
Cross-ventilation means opening windows or doors on different sides of a home so air can flow through. When outdoor air is cooler, this can help remove heat that has built up indoors. Studies of passive cooling in homes have found that night-time ventilation can reduce overheating, although effectiveness depends on the building, outdoor temperature, safety, noise and air quality.
3. Reduce heat from conservatories and sun-facing rooms
Conservatories can become very hot because sunlight passes through the glass and warms the surfaces inside. Keep them ventilated during the day and, where possible, close internal doors between the conservatory and the rest of the house. Reflective films, blinds, shutters, awnings and shaded roofs can all reduce heat gain.
Window shutters and retractable awnings in Mediterranean countries. (Professor Amin Al-Habaibeh, author provided) Professor Amin Al-Habaibeh, Author provided (no reuse)
Loft spaces and top-floor rooms can also become hot because roofs absorb solar heat. Loft ventilation or reflective roof materials may help in some homes, although these are usually more substantial interventions. For example, solar panels on the roof can generate electricity and at the same time act as a barrier to reduce heat transfer to the building.
4. Move where you sleep
If your bedroom is on an upper floor or faces south or west, it may be one of the hottest rooms in the house. Heat rises through the building, and sun-facing walls and roofs can continue releasing stored heat after sunset.
During a heatwave, sleeping on the ground floor or north-facing side of the home may help.
5. Reduce heat and humidity indoors
Ovens, hobs, tumble dryers, washing machines and dishwashers can all make indoor spaces warmer. Cooking and drying clothes indoors can also increase humidity, making it harder for sweat to evaporate.
On very hot days, use heat-producing appliances earlier in the day or later in the evening. Use extractor fans when cooking or showering because they remove warm, moist air before it spreads through the home. Research on moisture movement and extractor fans has shown that fans can reduce the movement of moisture from kitchens and bathrooms to other rooms.
6. Choose breathable bedding and clothing
A review of sleepwear and bedding fibre types found that bedding and clothing can affect thermal comfort during sleep. Light, loose sleepwear and bedding can help the body lose heat. Cotton and linen are often comfortable because they absorb moisture and allow air movement, although fabric weave, thickness and moisture handling also matter. Avoid heavy bedding, thick duvets and tight synthetic fabrics that trap heat and moisture.
7. Use fans carefully
Evidence on electric fan use in hot weather suggests that fans can be useful in many hot conditions, but their safety depends on temperature, humidity, age, hydration and health.
Fans do not cool the air. They move air across the skin, which can help sweat evaporate and make people feel cooler.
In very high temperatures, especially for older adults or people who are dehydrated or unwell, fans alone may not be enough. If using a fan, drink water, avoid directing it continuously at the face while sleeping, and stop using it if it makes you feel hotter, dizzy or unwell.
8. Try low-cost cooling aids safely
Reusable ice packs, freezer blocks or cooling pillows may help some people feel more comfortable. Wrap ice packs in a cloth or place them on a tray to avoid condensation soaking bedding or direct cold contact with skin.
Cooling mattress toppers and bedding that use water or phase change materials may also help. These materials absorb, store and release heat as they change state, although cost and effectiveness vary.
In hot weather, better sleep starts long before bedtime.
The most effective approach is usually a combination: block sunlight during the day, ventilate when outside air is cooler, reduce heat from appliances, sleep in the coolest room available and use bedding that allows the body to lose heat.
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