Parts of the UK were hotter than Marbella and Tenerife on Monday and sweltering temperatures are set to soar even higher on Tuesday.
The mercury was pushing 30C (86F) across London and the south-east, with Charlwood in Surrey recording a high of 29.5C (85.1F) by mid-afternoon, making it warmer than some of Europe’s top tourist destinations.
It came on the same day as the new rule of six was introduced making it illegal to meet in groups of more than six people indoors and outdoors in England.
It meant that large groups in parks were banned from meeting together to enjoy the sunshine.
Temperatures are expected to rise above 30C (86F) on Tuesday, far exceeding the September 20C (68F) average in London and the south east and 18C (64.4F) for the rest of the England and Wales.
It means parts of the south could pass the threshold for a heatwave, which requires three consecutive days of temperatures above 28C (82.4F), according to the Met Office.
This would be unusual as statistically 97% of UK heatwaves occur in the summer months of June, July and August.
Forecaster Luke Miall told the PA news agency: “Temperatures are quite high for this time of year.
“This is because of southerly winds pushing up from the continent along with a band of high pressure.
“And Tuesday will potentially be hotter, with parts of Scotland and Northern Ireland also witnessing clear skies and temperatures into the low-twenties.
“Most of Wales, northern England and the Midlands will also be in the high twenties.”
However the temperatures will still fall short of the highest September temperature ever recorded, which was 35.6C (96.08F) on September 2, 1906.
Cooler weather will return from Wednesday with temperatures dropping to the low 20s towards the end of the week, Mr Miall said.