Britain experienced its hottest June day for 40 years yesterday as the mercury hit 33.9C at Heathrow, the Met Office said.
It was the highest June temperature since the 35.6C recorded in Southampton on June 28, 1976, the hottest day of the year so far and the first time the mercury has hit 30C or over on five consecutive days in June since 1995.
While many have been basking in the sun, the heat has brought health warnings of toxic air in large parts of southern England and Wales. NHS England has urged the elderly, children and those with medical conditions to keep cool and hydrated during the heatwave.
Three people have died after getting into difficulty while attempting to cool off. Spencer Hurst, 15, died on Tuesday evening after failing to resurface when swimming in a lake near Walsall. On Monday, another teenage boy drowned in a reservoir outside Rochdale, Greater Manchester, and a woman in her 80s died after being pulled from the sea at East Wittering beach in West Sussex.
The heatwave has led to roads melting in some areas, and speed restrictions and cancellations on train lines due to the risk of tracks buckling.
Transport for London reassured concerned customers that softening of sealant on the capital’s tramline was harmless.
London mayor Sadiq Khan triggered the capital’s emergency air quality alert on Tuesday, with a warning that areas near busy roads would be particularly affected. Dr Taj Hassan, president of the Royal College of Emergency Medicine, said air pollution levels posed a “real threat to people’s health and will place extra stress on an already stretched NHS”.
Researchers said the toxic air was caused by high ozone levels brought up from industrial parts of France by a southerly wind. They also warned that particulate levels – from motor vehicles and other fuel burning – were expected to be “moderate, with high again a strong possibility”.
Simon Birkett, from the Clean Air in London campaign, said the government had failed to issue alerts in two areas where the ozone level had breached EU directives and two more had been delayed. He accused the department for environment, food and rural affairs (Defra) of trying to play down the health threat posed by air pollution.
However, Defra dismissed the claim, saying two alerts – for St Osyth, Essex, on Monday and Yarner Wood, Devon, on Tuesday – had been delayed because of “technical problems with the data feed from monitoring sites to the UK Air website”.
In the two other cases, Defra said neither had actually breached the trigger threshold, claiming one was right on the limit and the second was an erroneous.


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