People should take simple steps to stay safe to reduce the number of deaths caused by the heatwave, the UK Health Security Agency’s top scientist says.

Temperatures could reach 41C (106F) in England next week while the rest of the UK could also see new record highs.

A national emergency has been declared, and the UK’s first ever red extreme heat warning has been issued.

“In these exceptionally high temperatures everybody can be affected,” said Prof Isabel Oliver.

Asked whether thousands of people could die in the hot weather – as has been reported in newspapers – UKHSA chief scientific officer Prof Oliver declined to suggest a figure.

“It is very difficult to predict but I can tell you that we monitor this very closely,” she told BBC Radio 4’s Today programme.

“Last year we didn’t reach temperatures anywhere near the ones that are predicted for next week, [and] we saw over 1,600 excess deaths associated with the period of heatwave. So this is why we are keen that everybody knows what they can do to stay safe.”

Downing Street has said it will hold talks over the weekend, and a meeting of the Cobra emergency committee took place on Saturday.

The Met Office red warning – the highest level – is for extreme heat and covers an area including London, Manchester and York on Monday and Tuesday. It is the first time it has been issued since the warning system for heat started last year. It means:

* there is a danger to life and risk of serious illness, not just among the most vulnerable

* people will need to change their daily routines and working practices

* there could be disruption to power supply, water and even mobile phone signal

* increased risk of water safety incidents

* delays to road, rail and air travel

Rail passengers in England and Wales have been warned they should only travel if necessary, and Network Rail said speed restrictions were likely.

Some schools will also close early next week and some hospital appointments will be cancelled.

The rest of England, Wales and southern Scotland will be under an amber warning for extreme heat – while in Europe, deadly wildfires have broken out in Portugal, Spain and southwestern France.

BBC Weather forecaster Susan Powell said the situation was unprecedented.

She said there was an 80% chance the UK would break its current highest temperature record – 38.7C in Cambridge in 2019. Temperatures could reach as high as 41C in England on Monday, with 38C quite widely across England and Wales.

Tuesday is set to see highs of 40C, or above, in eastern England. Northern Ireland and Scotland could also see their temperature records broken, she said.

And on top of that, the temperature overnight on Monday into Tuesday could also hit a new peak – with highs of 25C expected.

“The problem is we have a 48 to 72-hour period where people who are vulnerable have no cooling-off period,” she said. “It’s super dangerous.

“And the areas of heat go right through to the coast. A lot of people take refuge at the coast, but it’s not going to be significantly cooler by the sea.”

As well as the Met Office warning, the UKHSA has issued its highest level four heat alert to health and care bodies – warning illness and death could occur “among the fit and healthy”.

The UKHSA’s Prof Oliver said the most vulnerable remain those in older age groups and those with long-term heart and lung conditions – but everybody was affected.

“The key message is that we can absolutely avoid those deaths and we can stay safe if we take simple measures – if we make sure that we take plenty of water, that we keep cool, that we avoid the sun when it’s hottest particularly between 11am and 3pm and that we look out for those who are most vulnerable,” she said.

People should avoid exercise, drink lots of water and make sure children are protected from the heat to reduce the pressure on nurses, the Royal College of Nursing said.

Most deaths during a heatwave are usually heart attacks or strokes caused by the strain of trying to keep body temperatures stable.

On Friday evening, NHS leaders warned there would be greater demand for ambulances – and patients should not be left in ambulances outside hospitals in hot weather for more than 30 minutes in the heat.

Exposure to extreme temperatures can be fatal.

An unprecedented three-week heatwave in northern France in August 2003 resulted in 15,000 excess deaths – those are deaths from all causes that occur above and beyond those expected under “normal” conditions.

The vast majority of the deaths were among older people, aged 65 and above.

In England during the same period, there were more than 2,000 excess deaths, compared to the previous five years.

The rise in mortality due to hot weather can happen very quickly, usually within the first couple of days of the temperature rising.

So the Met Office red heat warning and the UK Health Security Agency's level four health alert are like warning klaxons for the government, health service and individuals to make necessary preparations now in order to mitigate the risks.

Experts say that climate change is making heatwaves more likely as well as more intense and lasting longer.

The world has already warmed by about 1.1C since the latter half of the 18th century, and experts predict that temperatures will keep rising unless governments make steep cuts to emissions.

The hot weather is an “extra burden” for care homes, said Mike Padgham, the chair of the Independent Care Group which represents care providers

“Having adequate staffing to check on residents is a particular challenge,” he told the Today programme on Saturday, saying that care homes might have to ask relatives and volunteers to come in to help.

Carers will make sure curtains are drawn, move residents to cooler areas of the home, use water sprays and ensure everyone stays hydrated, he said.

Schools are also making preparations, with some headteachers considering whether to close.

Lee McConaghie, headteacher of Ashton-on-Mersey school in Greater Manchester, told BBC Breakfast that shutting was a last resort, saying: “Children have been out of education for too long.”

Currently, he plans to stay open, although school uniform rules have been relaxed. “At the end of the day it’s Shakespeare and trigonometry on Monday morning as normal,” he said.

There is concern that the hot weather might also lead to more people getting into difficulty while swimming – after a teenage boy died after getting into the water at a quarry in Lancashire last week.

“We’re not trying to take the fun out of the sun,” said Claire Gauci from the Canal and River Trust which has launched its safety campaign.

“We're just asking particularly teenagers and young people not to jump into locks, not to jump off bridges... If you really want to swim outside, find an open water swimming club.”

She said the water may be shallower or deeper than expected or there could be weeds and plants that can tangle around people’s limbs.

Meanwhile, firefighters are urging people to swap barbeques for picnics, in a bid to avoid triggering wildfires. (BBC)

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