A late Indian Summer will make Britain hotter than the Mediterranean.
The lockdown boost comes from a 700 mile-wide “subtropical burst”, which will push the mercury towards 20C this month.
Parts of the UK are due to enjoy temperatures of 18C on November 8 and 9, making it warmer than French port city Marseille (17C).
Heat from the Azores will bring 16C later in the week.
Most areas will have sunny spells at times, but there will be some cloud and showers in the West.
The Met Office forecasts “particularly mild” conditions lasting past mid-month.
But lower temperatures and snow are due to arrive from late in the month.
The highest November temperature on record in the UK is 22.4C, reached on the first of the month in 2015 in Ceredigion.
The Weather Outlook forecaster Brian Gaze said: “It’s notably warm for November – with 18C expected and feeling like an Indian Summer after frosts and snow. But computer models suggest colder weather from late November.”
Met Office forecaster Marco Petagna added: “An established mild southerly airstream could see 17C ahead, with the East drier and West having some rain.”
A Met Office insider said: “It’s likely to remain mild for the rest of the week and after, feeling particularly mild in any brighter spells.
"But temperatures possibly turn colder than average into December, with the chance of wintry showers, notably for the North.”
Members of the public were pictured enjoying today's sunshine on Primrose Hill, north London, in the first days of England’s second coronavirus lockdown.
People in England are still allowed to exercise outdoors in public places.