A national red alert heatwave emergency has been declared for most of England, including the South West London area, for Monday and Tuesday.

The Met Office has issued a red 'Extreme Heat' warning amid concerns that temperatures could reach a record high of 40C.

The organisation warned: "Exceptional, perhaps record-breaking, temperatures are likely on Monday, then again on Tuesday.

"Nights are also likely to be exceptionally warm for the UK, especially in urban areas. This is likely to lead to widespread impacts on people and infrastructure."

It added: "For the first time temperatures of 40C have been forecast in the UK and the Met Office has issued the first ever Red warning for exceptional heat.

"Exceptional heat is expected to affect a large part of England early next week, with temperatures likely in the high 30s C in some places and perhaps even reaching 40C."

Dr Agostinho Sousa, Head of Extreme Events and Health Protection at UKHSA, said: "Heat-health alerts have now been issued to the majority of the country, with temperatures set to remain consistently high throughout the duration of the weekend and the start of next week.

"It is important to keep yourself hydrated and to find shade where possible when UV rays are strongest, between 11am and 3pm.

"If you have vulnerable family, friends and neighbours, make sure they are aware of how they can keep themselves protected from the warm weather.''

Met Office Chief Meteorologist Paul Gundersen, said "Exceptional, perhaps record-breaking temperatures are likely early next week, quite widely across the red warning area on Monday, and focussed a little more east and north on Tuesday. Currently there is a 50% chance we could see temperatures top 40C and 80% we will see a new maximum temperature reached.

"Nights are also likely to be exceptionally warm, especially in urban areas. This is likely to lead to widespread impacts on people and infrastructure. Therefore, it is important people plan for the heat and consider changing their routines. This level of heat can have adverse health effects."

The step up in warning level to red is running parrel to an increase in the current Heat Health Warning to Level 4 for England by the UK Health Security Agency.

The high pressure near the southern half of the UK, which has been responsible for this week's warm weather, continues to dominate bringing largely dry and clear weather for most. However, during the weekend, a developing southerly flow will allow very high temperatures currently building over the continent to start to spread northwards into the UK. Further north, eastern areas of Scotland could see temperatures in in the high 20C in a few places, well above their average for the time of year.

This is the first time the Met Office has forecast 40C in the UK. The current record high temperature in the UK is 38.7C, which was reached at Cambridge Botanic Garden on 25 July in 2019.

Climate change is a factor, according to Climate attribution scientist at the Met Office, Dr Nikos Christidis.

He said: "In a recent study we found that the likelihood of extremely hot days in the UK has been increasing and will continue to do so during the course of the century, with the most extreme temperatures expected to be observed in the southeast of England.

"Climate change has already influenced the likelihood of temperature extremes in the UK. The chances of seeing 40°C days in the UK could be as much as 10 times more likely in the current climate than under a natural climate unaffected by human influence. The likelihood of exceeding 40°C anywhere in the UK in a given year has also been rapidly increasing, and, even with current pledges on emissions reductions, such extremes could be taking place every 15 years in the climate of 2100."