Experts are warning people not to use a fan in 35C conditions - just as sweltering heat has scorched the UK all week.

Highs of 29C have been seen in parts of the UK this week, especially in London and the South West, while even the north of England has enjoyed unseasonably warm weather.

While Thursday was the hottest day of the year so far, fortunately, the temperature has still been cool enough for fans to work. But if the temperature does get higher than it has been this week, electric fans will no longer be a good option-they will become ineffective and may actually do more harm than good, say experts. It might sound counterproductive, but fans aren't the answer when the heat gets really bad, for a very surprising reason.

British homes are awful places to be in a heatwave. That's because, due to our moderate climate and cold winters, they're designed to trap heat in, using heavy duty bricks, insulation, double or even triple glazing and thick roof tiles to keep as much of the heat inside as possible.

That's all great on a freezing December morning, but in the grip of a sweaty and humid spell, it can become a real struggle to battle through the hot conditions, especially as the vast majority of UK homes don't have air conditioning units.

Parts of the UK have seen temperatures nearly hit 30C on Thursday, such as in London, while even up north in Sheffield and Leeds, temperatures topped out at 28C, according to the Met Office - perfect fan weather.

But a fan isn't the answer when temperatures rise beyond 35C.

Using a fan during a heatwave can actually make your room even hotter. According to the Government's own heatwave plan, electric fans only work in temperatures under 35C.

The UK government's advice says: "Homes can overheat and become uncomfortable during warmer weather, particularly when you are trying to sleep.

"Use electric fans if the air temperature is below 35C, but do not aim the fan directly at your body as this can lead to dehydration."

But at any temperature, fans don't actually cool down the room, they simply move the air around. So, although you might feel a bit better with one in your face, the room is just as hot as it was before, and it could actually lull you into a false sense of security if you use a fan instead of staying hydrated or cooling the room properly.

The best thing to do is try to shade windows, increase airflow, but close curtains and keep cool with regular water or even cold showers, and stay out of direct sunlight.

It's going to be advice we keep returning to, as temperatures are only expected to keep getting hotter in future.

The government's own advice adds: "Climate change is already causing warmer temperatures in the UK. All of the warmest years on record in the UK have occurred since 2002, and in July 2022 temperatures exceeded 40C for the first time on record.

"It is estimated that 2,803 people aged 65 years and over died due to the heat in England in 2022, and it is predicted that the number of heat-related deaths per year may triple by 2050.

"Hot weather can increase the risk of heart attack, stroke, lung problems and other diseases. Older people, babies and young children are more likely to be unwell from hot weather because their bodies are less able to regulate temperature.

"People with underlying medical conditions can also be vulnerable to the effects of hot weather."

"Many of the harms linked to heat exposure are preventable if a few simple actions are taken. During the summer, UKHSA will work with the Met Office to issue alerts alongside the weather forecast if the weather is so hot that it has the potential to affect people's health, and will help you to take steps to protect yourself and others."