This is a significant temperature anomaly for the UK and the rest of western Europe, including Ireland, France, and Benelux. A general rule of thumb translates these temperatures to the ground with roughly 12-14 °C higher values to get an idea of peak temperatures at the surface. So we can expect that peak daytime well above +30 °C.
The first week of September results in temperatures back into the low 30s for London and the rest of southern and southeastern England. This happens due to an unusually strong heatwave intensifying over western Europe, associated with the Omega Blocking High and Heat Dome in the upper levels.