Britons may struggle to sleep when outdoor temperatures reach just above 23C during the day, according to new data.
Experts at the UK's Sleep Charity previously warned that many people experience restless nights when their bedroom temperature exceeds 24C.
However, a recent study by European indoor climate management specialists tado° shows that even lower daytime temperatures can lead to uncomfortable sleeping conditions.
Analysis of data from over 120,000 UK homes suggests that average daytime temperatures as low as 23C can result in nighttime indoor temperatures surpassing the threshold for comfortable sleep.
Met Office forecasts predict that London and the South-East will experience average daytime temperatures exceeding 23C on Thursday, with the South and East of England not far behind.
The Sleep Charity recommends an ideal bedroom temperature between 16C and 18C for optimal rest.
Higher nighttime temperatures have been shown to disrupt the body's natural cooling process, leading to increased restlessness and reduced sleep quality.
Christian Deilmann, CPO and Co-founder of tado°, said: "We all love the warm temperatures, within reason, during the day but it is surprising how an average temperature of just over 23°C can heat up your home to a point where you may face an uncomfortable night that stops you sleeping."
The study found that during last September's heatwave, Londoners endured a week of average nighttime temperatures at or above 24C, peaking at 26.2C on September 9. Other regions, including the East of England and the Midlands, also experienced multiple consecutive nights of high temperatures.
tado°'s data reveals that indoor temperatures remain more stable than outdoor temperatures due to home insulation, potentially leading to uncomfortable summer nights.
Mr Deilmann added: "We all spend a lot of attention on the heating systems of our homes and trying to reduce our energy consumption for it but less on how to keep cool."
The company suggests that smart air conditioning controls can help manage energy consumption and costs during hot weather, with potential savings of up to 22 per cent on average.
A yellow heat-health alert has been issued as temperatures hotter than those forecast for Ibiza are set to sweep London this Friday.
The alert is in place from 5pm on Thursday in the capital, where it's set to reach a sizzling 32C on Friday, and remains in place until 11pm on Saturday.
