The UK is in the middle of yet another heatwave, with parts of the country expected to bake in temperatures of up to 34°C. 

So, what's behind this intense heat?

According to the Met Office, the UK has been caught between two air masses. 

An expanding plume of warm air is creeping north from continental Europe, causing temperatures to rise in southern and eastern parts of the UK. 

At the same time, low pressure is feeding the northwest with cloud, rain, and fresher air. 

'This sets up a sharp contrast across the UK, with a so–called baroclinic zone – a boundary between warm and cool air masses – positioned across or close to the country,' the Met Office explained.

'Along this boundary, weather fronts will develop and move slowly, bringing outbreaks of rain, particularly to northern and western areas. 

'This will result in a "waving" front, where bands of rain ebb and flow over similar areas over several days.'

The plume of warm air in the southeast of the UK is being driven by a strong area of high pressure over continental Europe.

The Met Office said: 'This high pressure is promoting widespread sinking air, which suppresses cloud formation, allows for prolonged sunshine and leads to increasing temperatures through compressional heating.'

Over the next few days, temperatures will creep up across southern and eastern areas, potentially reaching the low–30s by Monday. 

However, it's not all doom and gloom for Brits in the northwest. 

As we go into the weekend, the influence of high pressure from Europe is expected to edge further north. 

This will bring more settled and drier conditions to many northern areas, along with a rise in temperatures and more widespread sunshine.

As temperatures climb, the air will also become increasingly humid – increasing the risk of thunderstorms, particularly for Brits in eastern England. 

'If storms do occur, they could be locally intense, bringing heavy downpours, strong gusts and frequent lightning,' the Met Office said. 

'However, it is important to emphasise that thunderstorms are not guaranteed, and their exact timing and location remain uncertain.'

The news comes shortly after experts warned that extreme heat is becoming Britain's new normal. 

However, Professor Andrew Charlton–Perez, professor of meteorology and Head of the School of Mathematical, Computational and Physical Sciences, University of Reading, said: 'It's perhaps a sign of how much our perception of hot weather has shifted that 27 or 28 degrees for south east England no longer feels particularly warm.

'In Reading, less than 1 in 10 June days are typically as warm as this since 2001. 

'That's partly because the likelihood of similar temperatures has approximately doubled since the latter decades of the 20th century.

'We know there can be significant impacts of hot weather for those who have pre–existing conditions that make them particularly vulnerable, so I would encourage people to pay attention to the UKHSA warnings and take action to prepare themselves and others.'