September heatwave: UK could experience hottest day of the year as temperature climbs  

The UK is likely to experience the hottest day of the year this week.

The mercury could climb to 32 degrees Celsius in the south of England today, with temperatures set to remain high over the weekend.

The sweltering weather has triggered an Amber heat health alert, with authorities urging the public to stay hydrated and check on vulnerable people and pets.

The health alert - issued by the UK Health Security Agency from 2pm on Monday - will last until 9pm on 10 September.

“There’s a chance the highest temperature of the year so far of 32.2°C on 10 June could be exceeded this week, most likely in the southeast where one or two places could see 33°C,” the Met Office has reported.

So why is it so hot in the UK - and is climate change to blame?

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Where in the UK is experiencing a heatwave?

A location is classified as experiencing a ‘heatwave’ when it meets the daily maximum temperature threshold for three days in a row.

This threshold is between 25°C and 28°C depending on where you are in the UK. On Tuesday, areas of West Yorkshire, Cornwall, Devon and Wales reached local criteria.

North England and Scotland were cooler, but temperatures are still high by regional standards.

The hot weather will ease on Sunday and Monday, with a “thundery breakdown” likely in some parts of the country.

“A cold front will begin to influence things from the northwest towards the weekend, though it’ll remain very warm or hot in the south,” Met Office Deputy Chief Meteorologist Steven Keates said.

"There’s a chance the thunderstorm risk to western areas from Friday onwards may require a warning response, with some potentially impactful downpours.”

Why is it so hot in September and is climate change to blame?

Such sweltering temperatures are unusual for this time of year in the UK. Wednesday was the hottest September day since 2016.

So is climate change to blame?

This particular hot spell is driven by tropical storms pushing high pressure over the UK, the Met Office said.

The tropical cyclone season in the North Atlantic has pushed the jet stream - a core of strong winds - to the north of the UK.

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When atmospheric pressure increases, it means that air will sink, compressing as it falls. On average, air temperature increases by 1°C for every 100m that it plummets.

But global warming is also increasing the intensity and frequency of heatwaves. The average temperature over the last decade in the UK has been 0.8°C warmer than the 1961-1990 average. All of the UK's 10 warmest years on record have occurred since 2002.

In July 2022, UK temperatures exceeded 40°C for the first time on record.

Such scorching weather is likely to become the norm.

By 2070, the Met Office predicts that Summer will be between 1 and 6°C warmer and up to 60 per cent drier.