Today could be the hottest day of the year so far, with temperatures soaring to as high as 32C (89.6F), forecasters said.
Large areas of Britain will bask in sunshine with the hottest regions being in east and south-east England, which will see temperatures rivalling those of the Caribbean.
Most of the UK will see temperatures in the high 20s, albeit with some showers in the west and Wales and cooler temperatures in Scotland and Northern Ireland, according to MeteoGroup, the weather division of the Press Association.
The hottest day of 2012 recorded so far was on July 25, when it reached 31.4C (88.5F) at the Olympic Park in east London.
MeteoGroup forecaster Gemma Plumb said: "There is the potential for it to be the hottest day, with the highest temperatures expected to be across East Anglia, south-east England and parts of the East Midlands.
"Temperatures will be between 29C (84.2F) and 31C (87.8F) but I can't rule out it reaching 32C (89.6F)."
The Caribbean islands are currently experiencing temperatures of between 30C (86F) and 32C (89.6F), she added.
It will mean a warm start to the Premier League season today. Games taking place include Arsenal v Sunderland at the Emirates, Newcastle United v Tottenham Hotspur at the Sports Direct Arena and West Bromwich Albion v Liverpool at the Hawthorns, while West Ham mark their return to the top flight at home to Aston Villa at Upton Park.
It is also set to be a hot third day of the test match at Lords today between England and South Africa.
Other events taking place this weekend include the V Festival at Hylands Park, Chelmsford and Weston Park, Staffordshire, with headline sets from The Stone Roses and The Killers and other bands including Rizzle Kicks, The Enemy, Pixie Lott, Dappy, The Human League and The Proclaimers.
Cyclists from the Team GB para-cycling team are due to take part in a 20km time trial at Blenheim Palace in Woodstock, Oxfordshire today as a warm-up for the Paralympic Games.
There will be more unsettled weather in western areas, which yesterday saw up to 40mm (1.5in) of rain in some places. Northern Ireland and Scotland will struggle to top 22C (71F) today.
Tomorrow will present a more unsettled picture across much of the UK with showers spreading northwards over much of the UK, some of which could be heavy and thundery, Ms Plumb said.
But temperatures could still reach 30C (86F) in London and 26C (78.8F) in other parts of the country, according to MeteoGroup.