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.
