The Met Office warning, issued on Tuesday morning (August 11), will come into effect at 9am on Thursday, August 13, and last until midnight. The fresh heatwave could see temperatures as high as 37 or even 38 degrees, the Met Office said. The sweltering temperatures "may lead to impacts on transport, infrastructure and health", the Met Office said. "Some changes in working practices and daily routines [will] likely be required," the Met Office advised. The areas covered by the warning include London and the South East, the East, the West and East Midlands, and Yorkshire and Humber.