The youngsters, aged two and four, were found in their family car in a residential parking lot in the southern town of Carpentras, where investigators said they believed the heatwave was the most likely reason for the deaths.The latest bout of exceptionally high temperatures to hit Europe has seen outdoor events cancelled, transport disrupted, schools shut and office workers told to work from home, as the authorities issued health alerts to protect the elderly and vulnerable.France, at the epicentre of the weather anomaly, has been sweltering for days.But Britain's Met Office on Monday issued a rare red warning for extreme heat -- the national weather agency's highest alert level, indicating risk to life and the possibility of major infrastructure such as roads and railways being closed.It was only the second time the Met Office has ever issued a red warning for heat, with temperatures in the shade expected to rise as high as 38 to 40C on Wednesday and Thursday.The warning runs from 9:00 am (0800 GMT) on Wednesday to 9:00 pm on Thursday and covers a large area of central and southern England, including London and Birmingham, the UK's two largest cities.Multiple schools in southwest England said they were planning to finish the school day early because of the anticipated temperature spike, and a train company said it was cancelling or changing some of its services out of London due to the "severe weather".Akshay Deoras, a senior researcher at the University of Reading's National Centre for Atmospheric Science, in England, said it was clear what was behind the rash of heat records.