London, 15 July 2022 (dpa/MIA) - Britain's Met Office has issued its first red warning for extreme heat, warning of a "potentially very serious situation" in parts of England next week. Forecasters say there is an 80% chance of the mercury topping the Britain's record temperature of 38.7 degrees, set in Cambridge in 2019, with the current heatwave set to peak on Tuesday. Met Office spokesperson Grahame Madge said there is a 50% chance of temperatures reaching 40 degrees somewhere in Britain, likely along the A1 corridor, a highway linking London to Edinburgh. Britain's Health Security Agency has increased its heat health warning from level three to level four - a "national emergency." Level four is reached "when a heatwave is so severe and/or prolonged that its effects extend outside the health and social care system ... At this level, illness and death may occur among the fit and healthy, and not just in high-risk groups," it said. Madge added: "We've just issued a red warning for extreme heat for Monday and Tuesday which is the first such warning ever issued. "The warning covers an area from London up to Manchester and then up to the Vale of York. This is potentially a very serious situation." He said computer modelling had been "firming up around just how intense the heat will be for Monday and Tuesday, with the emphasis on Tuesday. "It's now considered 80% chance we will see the all-time UK record broken," Madge said on Friday morning. "There's stronger indications now of 50% chance of seeing 40C being observed somewhere in the UK, and most likely that would be within the red warning area for extreme heat. "Probably the most likely areas to look at would be north of London and up to Lincolnshire, inland. He said temperatures reaching 40 degrees would be "historic." "If we get to 40C, that's a very iconic threshold and shows that climate change is with us now," he said. "This is made much more likely because of climate change."