The Met Office says Thursday is expected to see warm and sunny weather for many parts as the mercury will hit highs in the mid-20s in some areas, particularly in the south.
Brits are set to bask in hotter temperatures than Portugal, with a brief hot blast in the coming days.
Forecasters expect a wet weekend, with torrential rains and strong winds that will blast the country over the weekend.
As temperatures rise to the mid-20s, Thursday will be sunny and warm in many parts of the country.
It will bring the temperature up to 22C, which is what Faro in Portugal is expecting.
Met Office forecaster Aidan McGivern said the UK has been “much warmer than average for the first half of September.”
In his forecast, he said: “That theme continues for the first day of this forecast, Thursday.
“There’ll be fog patches first thing and poor visibility on the roads, but once the fog clears, most places will have a fine day, with warm sunny spells.
“It’ll be 23 or 24C in the south and the high teens for the north.
“There’s more good weather on Friday with warm sunshine in parts of England, Wales, and eastern Scotland.
But the warmer weather is likely to give way to heavy rain by the weekend, forecasters warned.
According to the Met Office’s long-range forecast, the weekend will see heavy rains that will be worst in the south.
There will be some sunshine and brighter spells, but rain is expected in many places. This could pose a threat of flooding.
UK Weather Forecast
Today:
Fog patches soon clearing, then most parts dry with broken clouds and sunny spells. It is possible to have a light shower. You will feel warm even in light winds, particularly in the south or southeast. Windy and wetter in the northwest.
Tonight:
Windy in the northwest with spells of rain across Northern Ireland and Scotland. Clear spells will be found in the south and east. There may be some fog and low clouds.
Friday:
Western areas were cloudy, with outbreaks of rain moving slowly east, heavy in places. Broken clouds, sunny spells, and dry conditions are common in the eastern and central parts of the country.