Scorching heat and sunshine will give way to average temperatures and bursts of rain before the end of the week, forecasters warned today.
While parts of Britain look set to enjoy highs of around 28C (82.4F) today and tomorrow, it will feel noticeably cooler by Thursday, experts said.
Aisling Creevey, a forecaster at MeteoGroup, the weather division of the Press Association, said: "Today will be another hot day, particularly in the South East.
"We are generally expecting temperatures of 28C, but might get little pockets of 29C and 30C in sheltered areas with low winds."
However, Scotland, Wales and northern and south-west England could see rain, which will be largely confined to Scotland as the day draws to a close, she said.
"By tonight it will be dry in most areas, with perhaps some misty conditions developing, particularly across northern areas.
"London will have temperatures of 15C or 16C, and more widely it will be 12C and 14C."
Another warm day is expected tomorrow. Cloud and showers could hit northern England, Scotland and parts of Wales, but the South East is expected to enjoy temperatures of 27C and 28C.
Ms Creevey added: "That day-time heat in the south-east could spark off heavy showers locally, with possibly a few rumbles of thunder.
"We are looking at Thursday where everything is going to change.
"It will go from fine and settled to cloudy with bursts of rain and temperatures dropping to average. It will feel noticeably cooler - between 19C and 23C."
Yesterday, the mercury hit 28.1C in St James's Park and Kew Gardens in London making it hotter than many holiday destinations.
Temperatures reached just 16C in Cape Town and 15C in Johannesburg. In Melbourne the highest recorded temperature was 17C and in Sydney it was 22C.
In Rio de Janeiro the mercury hit 24C and New York was only slightly warmer than London at 30C.
However not all of the country enjoyed such balmy weather. There was rain in northern Scotland, which moved across to north Wales and the north east of England.