The country has sweltered on the warmest day of the year, with the mercury reaching 29C at Heathrow and Kew Gardens.
Thousands of spectators made the most of the hot weather to watch Andy Murray win the men's singles final at Wimbledon.
Tennis fans at SW19 felt the heat with people suffering from a variety of weather-related ailments.
"We've had a busy weekend at Wimbledon, with the hot weather contributing to ailments including dehydration, sunburn and heat exhaustion," Katherine Eaton, regional events manager for St John Ambulance London, said.
"Our volunteers are determined to be the difference by making sure that everyone has access to essential first aid; and we would like everyone who is visiting to make themselves aware of where they can seek help should they begin to feel unwell."
Beaches up and down the country were also packed, leading to more than 250 call outs to the Coastguard.
Visitors to Victoria Park in east London were able to cool down in five-metre high water jets as a Guinness World Record was made for the largest ever residential water sprinkler.
Today's heat follows highs of 27.5C at London's Heathrow airport on Saturday afternoon. It put the previous high of 27.2C, also at Heathrow last month, in the shade.
Sky News Weather Presenter Sarah Pennock warned: "There will be plenty of sunshine across England and Wales - but if you are enjoying the outdoors prepare for high UV levels and a high pollen count."
Pennock said it will remain warm this week in much of England and Wales, although North Sea coastlines will turn cooler from Tuesday with an onshore breeze.
It means the UK is on course to enjoy its longest spell of hot weather since 2006, when temperatures were above 28C (82F) in many areas for around a fortnight.
The average maximum temperature in England at this time of year is 20.9C (69F).