The ECMWF weather model initially shows maximum possible temperatures of 26C on the evening of 22 May. The hottest conditions are forecast just south of London, though the mercury could climb to 23C or 24C across parts of Wales, central England and the east as well.

On 23 May, weather maps indicate highs of 27C across the south-east, with 26C expected in the Midlands. Temperatures of 24C are anticipated across most of England south of Yorkshire, according to the data. South Wales could also bask in highs of 25C.

The ECMWF model projects highs of 26C along the south coast of England on 24 May. Comparable temperatures are once again expected in the West Midlands and around London. Parts of southern Scotland could also enjoy 22C warmth at around 6pm.

On 25 May — marking the conclusion of the four-day warm spell — highs of 25C are possible across southern and western regions. The maps reveal that 18 counties could experience highs of 25C or above throughout the four day.

Met Office weather forecast for May The Met Office has indicated that temperatures could turn "rather warm" towards the end of May - particularly across southern regions. The Met Office forecast for May 17 to 26 states: "As this period progresses, high pressure is likely to begin to build from the south bringing more in the way of settled weather.

"Temperatures likely cooler than average to begin, but tending to recover as the period progresses, perhaps becoming rather warm by the end of the period, especially in the south."

When is a heatwave declared in the UK?

Whether an official heatwave will be declared this month remains to be seen. An official heatwave is confirmed when temperatures meet or exceed the heatwave threshold for three consecutive days.

The heatwave threshold ranges from 25C to 28C across the UK. It sits at 28C across the south-east of England, where temperatures tend to be at their highest, dropping to 25C the further north you travel.