ITV News Health and Science Correspondent Martin Stew reports from Southend as much of England swelters in 30C plus temperatures
September's heatwave is likely to peak on Saturday with temperatures rising as high as 33C in London, the Met Office has said.
It is likely to be the hottest day of the year, though further north will be cooler, and could beat the previous one set in June at 32.2C, with the UK Health Security Agency issuing an amber warning for heat until Sunday evening at 9pm.
This means weather impacts are likely to be felt across the health service, with those aged above 65 or those with pre-existing respiratory or cardiovascular disease at greater risk.
Although temperatures have risen this high before in September, it is unusual for the heat to last so long, with the Met Office predicting five to six days above 30C for some areas.
The heatwave is being driven by tropical storms pushing a high pressure system over the UK, with the jet stream having moved to the north and bending into what is known as an omega blocking pattern.
This system occurs when an area of high pressure gets stuck between two areas of low-pressure to the west and east and also slightly south.
This has brought torrential rain and flooding for Spain and Greece but hot, dry and clear conditions for the UK and central Europe.
How to stay safe in the sun:
Keep out of the sun at the hottest time of the day, between 11am and 3pm
Exercise when it is cooler such as the morning or evening
Keep your home cool by closing windows and curtains in rooms that face the sun
Cover up with suitable clothing such as an appropriate hat and sunglasses
Drink plenty of fluids and limit your alcohol intake
Check on family, friends and neighbours who may be at higher risk of becoming unwell, and if you are at higher risk, ask them to do the same for you
Symptoms of heat exhaustion, according to the NHS, include tiredness, dizziness, headaches, feeling sick or excessive sweating, as well as limb cramps and a high temperature.
If you suspect someone has heat exhaustion, move them to a cool place and remove unnecessary clothing like a jacket or socks.
You should also get them rehydration drinks and try to cool their skin.
The highest UK September temperature ever recorded stands at 35.6C.
The Met Office defines a heatwave as three consecutive days of a particular region exceeding a given threshold, which varies around the UK.
For Scotland, Wales, Northern Ireland, Cornwall and northern England, the threshold is 25C; for Somerset, Hampshire and the Welsh Borders, 26C; the south coast, East Anglia and the East Midlands, 27C; and for London and the home counties the threshold is 28C.
Met Office chief meteorologist Neil Armstrong said: “An active tropical cyclone season in the North Atlantic has helped to amplify the pattern across the North Atlantic, pushing the jet stream well to the north of the UK, allowing some very warm air to be drawn north.
“It’s a marked contrast to the much of meteorological summer, when the UK was on the northern side of the jet stream with cooler air and more unsettled weather.”
The amber alert is in place for: the East Midlands, the West Midlands, North West, South East, South West, East of England, London, and Yorkshire and The Humber.
Forecasters urged Britons prioritise their physical health in extreme weather.
Scientists are seeing heat records broken on a near-continuous scale, with the Earth having just experienced its hottest ever Northern Hemisphere summer, the World Meteorological Organisation announced on Wednesday.
Not only was it the hottest August on record, but it was the almost the hottest month ever measured, second only to July.
The average global temperature last month was 1.5C higher than the pre-industrial average, though this does not mean the target of the Paris Agreement has been breached as that refers to a decades-long average.
Last month also saw the highest global sea temperatures ever recorded, at an average of 21C.
Want a quick and expert briefing on the biggest news stories? Listen to our latest podcasts to find out What You Need To Know...