The Met Office has predicted the heatwave will end next week as temperatures will become ‘more normal’.

Looking ahead from September11 to September 20, the Met Office said: ‘The last of the warmth and humidity will probably still be lingering across some south-eastern parts of the UK at the start of the period.

‘However, a cold front, already making inroads in the northwest will erratically move southeast across all parts, introducing cooler, fresher conditions.

‘Thereafter, conditions across the UK are expected to become generally more changeable with temperatures likely to return to closer to normal.’

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 would 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.

A sunny summer day with high temperatures during a heatwave in London (Picture: Nicolas Economou/NurPhoto via Getty Images)

There is also a chance of tropical nights in the south, defined as having temperatures over 20C, with Wednesday and Thursday night threatening to break the September night time record of 21.7C.

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.

Named after the Greek letter omega because of its shape, 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.

Beachgoers enjoy the sun and sea on Gyllyngvase Beach(Picture: Hugh R Hastings/Getty Images)

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 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.

As the climate continues warming because of rising greenhouse gases, these hot spells will become more frequent and severe, the Met Office said.

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Conditions are expected to become ‘more normal’.