Saturday's record temperatures not beaten
Suggestions that Sunday could beat Saturday's top 2012 temperatures in some UK areas have not been borne out.
South-east and east England experienced the hottest day of the year so far on Saturday when temperatures peaked at 32.4C (90.3F) in Suffolk.
Higher-than-predicted amounts of medium-level cloud on Sunday reduced the heat.
The Met Office has issued a yellow weather warning for heavy rain across large parts of England.
Temperatures are expected to return to average August levels next week.
The BBC weather centre said the highest temperature recorded so far on Sunday was 30.9 (87.6F) in Cambridge.
BBC forecaster Steve Cleaton said: "A little more medium-level cloud than we thought has kept temperatures a little lower than Saturday. Extra showers have also had an effect on the temperature," he said.
And the weather centre also said heavy showers have hit parts of southern England and London and were likely to cross into Kent and Sussex on Sunday afternoon.
Parts of north Wales and the Midlands have been hit by more persistent heavy rain, which will move across the Midlands as Sunday progresses.
The Met Office has issued a yellow warning for parts of the West Country, Midlands, east and north-east England , urging the public to be prepared for isolated heavy and thundery downpours.
"The Midlands and parts of eastern England are perhaps most at risk. The heaviest storms may be accompanied by hail and strong gusts of wind.
"Additionally, areas of heavy rain will develop across parts of northern England during Sunday afternoon and evening, although lacking the intensity of the storms further south," the Met Office said.
Forecasters have also warned of the risk of "localised surface water flooding and possible disruption to travel" in the worst hit areas.
Conditions north of the band of rain, in Northern Ireland and Scotland, are likely to remain largely dry and bright with cooler temperatures and a fresher feel.
Temperatures across much of the South East of England and East Anglia on Saturday were on a par with popular holiday destinations such as the Caribbean islands.
The hottest temperatures were in Suffolk. The village of Cavendish peaked at 32.4C (90.3F), Charsfield recorded 31.4C (88.5F) and Santon Downham basked in 31.3C (88.3F).
However, not all of the country had such high temperatures. Newquay, in Cornwall, only reached 18C, while Belfast registered 19C and Glasgow 20C.
Cardiff and Manchester reported temperatures of 21C and Carlisle was at 18C.
A weather front dividing the country marks the line between fresher weather to the north west of the UK and hotter, more humid weather to the south east.
The warmer parts of the UK were hotter on Saturday than such holiday destinations as Lanzarote in the Canary Islands, which was 29.8C.
It was also very hot in parts of France and Italy, with Paris experiencing highs of almost 39C and Florence 38C.