England and Wales basked in scorching temperatures on Saturday as the hottest day of the year so far arrived.
But the heat has prompted warnings from health authorities urging the public to take care in the potentially "dangerous" heatwave conditions.
Temperatures are predicted to get as high as 32C (89.6F) in the south-east, with the majority of England and Wales still sizzling at between 28C (82.4F) and 31C (87.8F).
The continued hot spell shows no sign of ending as temperatures are set to remain in the mid to high 20s well into next week.
A warning issued by the Met Office has been escalated to a level three alert for Yorkshire and the Humber after temperatures have already reached heatwave conditions.
Level two alerts are in place across most of England preparing the public for the possibility of heatwave conditions, which it says can have a significant impact on health.
"Heatwaves can be dangerous, especially for the very young, very old or those with chronic diseases," the alert said.
A spokesman for Public Health England (PHE) said: "Level two alerts are triggered as soon as the Met Office forecasts that there is a 60% chance of temperatures being high enough on at least two consecutive days to have a significant effect on health.
"This will normally happen two to three days before a heatwave is expected to occur. As most deaths occur in the first two days, this is an important stage at which to ensure readiness and swift action to reduce harm from a potential heatwave."
Dr Angie Bone, head of the PHE's Heatwave Plan, said: "Everyone can enjoy the sun safely by keeping out of the heat at the hottest time of the day, avoiding sunburn and staying hydrated with plenty of cool drinks.
"The elderly and those with long-term illnesses are particularly vulnerable to the effects of very hot weather, so it's important to look out for them and keep indoor areas as cool as possible."
Gareth Harvey, a forecaster with MeteoGroup, the weather division of the Press Association, said the top temperature of the day will probably be recorded west of London.
"It's been a very hot spell of weather and today will be the hottest day so far.
"It's likely to hit 32C in the south-east, and be up to 31C across the rest of England and Wales.
"The hottest part of the day will probably be around 3pm to 4pm.
"There heat will bring a chance of brief thunderstorms in the east of England but only a few areas will see showers.
"The temperature will drop slightly on Sunday but remain hot and dry."
The North of the UK has seen the best temperatures over the last few days, with the highest recording of 29.2 degrees in Branham, Yorkshire on Friday.
The hottest temperature of the years so far was 29.9C (85.8F) in Edenfel, County Tyrone in Northern Ireland on Monday.
However temperatures will be markedly cooler in Northern Ireland and Scotland over the next few days, settling around 20C (68F).
The heat could lead to a few local thunderstorms in the east of the country.
The RAC said more than 11 million motorists were planning to hit the road this weekend.
Popular spots include the Lake District, Devon and Cornwall, the south coast of England, and Yorkshire.
The RAC added that it was boosting the number of its patrol teams following a sharp rise last weekend in hot weather-related breakdowns.
Emergency Services personnel warned against the temptation to cool down in the current hot spell by swimming in open waters after three people died in the West Midlands in the last week.
The body of a man, believed to be in his 20s, was yesterday pulled from the waters at Gullet Quarry, near Malvern in Worcestershire, in the same place where a teenager died last weekend.
Shortly before 7pm, the body of a man was recovered and he was confirmed dead at the scene, a spokesman for West Midlands Ambulance Service (WMAS) said.
It was the same water in which 17-year-old Russell O'Neill, from Worcester, died last Saturday.
He had been swimming at the quarry when he failed to resurface. His body was recovered by a dive team from South Wales Police at around 4.50pm.
It is the third open-water related death in the region after the body of a man was yesterday recovered from the River Severn in Bridgnorth.
John Woodhall, a water rescue specialist with WMAS, said people needed to be acutely aware of the dangers of swimming in open waters.
Yesterday was his second call to the quarry within a week, and he urged people not to be tempted to swim in the cool waters.
He said: "I've been here twice now. How many more people need to die before someone takes notice of our warnings of the dangers of swimming in open waters?
"After the first death I was back here at the quarry doing a TV news interview about it.
"The dead man's friends were laying flowers and, despite warning a man walking past me not to go into the water, he still did.
"He walked past the tributes on the way. I must have counted 20 people still swimming there.
"Quarries are not like swimming pools. The water is much colder. You go from 28 degrees outside to 10 degrees in the water. You can get muscle cramps and stitches.
"The bottom is uneven, there are no depth markings.
"Even strong swimmers can slip underwater and you may not make it back up again.
"Sadly, this is something that has now happened three times."
Hereford & Worcester Fire and Rescue Service Group Commander George Marshall warned against people using open waters as a place to cool down on hot days.
He said: "The water may look enticing but even on a hot day it can be extremely cold, leading to sudden cramp, and subject to strong currents which can catch out even the strongest of swimmers.
"There could also be obstacles and other debris hidden under the water which could trap or injure someone.
"Many pools and quarry lakes are also very deep and certainly not safe to swim in.
"Please think twice about going into open water and if you must take a dip please do it in the safety of a public swimming pool where there are lifeguards on duty."
Superintendent Ivan Powell of West Mercia Police echoed Mr Marshall's message.
He said: "This latest death also appears to be a tragic accident and our thoughts are with the man's family and friends.
"The shocking events of the past week bring into sharp focus the dangers of open water.
"Particularly in view of the current hot spell we would urge people not to go into rivers, lakes, ponds and canals to try to cool off.
"People need to recognise the risks associated with water and act responsibly.
"Bearing in mind that the summer holidays are fast approaching we would also ask parents to monitor where their children may be playing and also speak to them about the dangers."
Retailers reported rocketing sales because of the baking conditions.
Asda said sales of barbecues soared - 204% in the last two weeks, plus charcoal and fuel up 176%.
The supermarket also said shoppers were keen to cool off with paddling pool sales up 446% and sales of garden furniture blossoming 44% as Britons dine al fresco.
Burger sales were expected to rocket 300%, with ribs increasing by 200%.
Last weekend alone Asda sold three million sausages and 1.4m burgers, which when stacked on top of each other would cover the length of the London Marathon (26.3 miles).
Tesco predicted it would sell nine million sausages this weekend and sales of its summer fruits rocketed.
Many shoppers were avoiding stressful, sweaty trips to the shops instead sparking an internet frenzy splashing thousands on supplies.
Online retailer Amazon said compared with this time last year sales increased by 816% for paddling pools; 519% for sprinklers and sprayers; 543% for patio chairs and loungers and 145% for sun skincare products.
David Jones, Waitrose supply chain director, said: "When temperatures reach the 'tipping point' of 28 degrees we see customers switching from ice creams to ice lollies and from fizzy pop to mineral water based drinks as rehydration becomes more important.
"Many are virtually abandoning their stoves for the great outdoors - with barbies, salads and picnics foods on the menu.
"Ice lollies will be up around 110% on last year and charcoal likely to be up by 300% on last year."
Superdrug said this week was its biggest so far this year for suncare sales.
The company's buying director Simon Comins said: ""While we may moan about the British weather as soon as the sun comes out we certainly embrace the arrival of some summer heat.
"Our sales prove that sun starved Brits were eager to get out into the sunshine.
"As the forecast continues to show sun and high temperatures our stores will be offering sun protection, and after-sun lotion, bronzers to tan up faces and bodies for those that have to work and can't spend the week in the sun, and plasters for those inevitable blisters from a summer shoe's first airing."
Britain's bookmakers fear their liabilities on the mercury hitting the 100F mark (37.7C) could soon reach £1 million, as punters continue to place their bets.
Coral has already been forced to cut the odds several times in the last week, with the odds on 100F being reached down to 4-1, while a new record high is down to 8-1, from 10-1.
Coral's David Stevens said: "We know that 70% of us check the weather forecast at least once a day suggesting we might be obsessed by it - that's why we have seen a record number of hot weather related bets.
"With the high temperatures forecast to last, bookmakers could face a £1 million payout across the industry if the magic 100F is reached."
But the soaring summer temperatures have been a welcomed by tourism and business bosses in Wales, where trade has shot up dramatically,
Llangollen's international eisteddfod, which runs until Sunday, has recorded a 40% rise in visitors.
And department store John Lewis in Cardiff reported sales of outdoor furniture and barbecues tripling.
The store's managing director Chris Earnshaw said: "This week's hot weather has resulted in good sales for all things summer.
"Recent sporting events such as Wimbledon and the Lions tour have encouraged customers to get active outdoors with sports equipment seeing sales increase by 60% against last year.
"And outdoor furniture and barbecues have been extremely popular this week.
"Our sales have increased by an amazing 340% versus last year."
And the clear skies and sunny weather also mean good news for the 120,000 people expected to turn out to watch the Wales National Air Show in Swansea - where the famous Red Arrows display team will show off their skills.