Britain will be hotter than Barbados today. But don't panic. Just turn off all the lights, close the curtains, and hide under the sofa with bottles of iced water and fans. It'll all be over be over soon.
The mercury soared as temperatures peaked at 29.1C (84.4F) in London, while much of Scotland, Wales and Northern Ireland also saw temperatures in the mid-to-late 20s.
The Met Office said the conditions at Hampton near Richmond passed 2014's previous high of 28.7C, set two weeks ago. But with an Iberian weather pattern expected to descend on the UK overnight, forecasters have warned tomorrow could get even hotter.
Go to the beach? Take a swim? Enjoy ice-cream and water fights in the garden. Nope, stay indoors, is the advice from the Met Office and Public Health England. Britons in the South East, East and Midlands should keep out of the sun into between 11am and 3pm, ie, much of the daylight hours, the Met Office has warned.
But where to go? Public Health England have the answer. Don't exert yourself. Stay in your house, keep the non-essential lights and electrical equipment off to avoid generating more heat, and wear a hat or light scarf if "venturing" outdoors. Presumably, that's how people in Barbados live all year round.
People should "drink water" and "eat salad" too, said PHE, according to the Telegraph.
And schools should monitor overweight children, the advice, rather cruelly, adds. Muslims are also advised to stay indoors (the EDL will be pleased) if they are fasting because the heat could affect them more rapidly.
Of course it's hot-it's Summer!July 17, 2014
#Heatwave for many of us starts here. Hot & humid. uncomfortable, sleepless nights. you might need to find that fan you bought in 2003.— Lucy Verasamy (@LucyWeather) July 17, 2014
“While many people enjoy hot weather, high temperatures can be dangerous, especially for people who may be particularly vulnerable, such as older people, young children and those with serious illnesses," Dr Paul Cosford, of Public Health England said, joylessly.
“During hot weather it’s important to balance food and fluid intake between fasts and especially to drink enough water.”
The Sydney Morning Herald gave the British experts a not-underserved gentle ribbing for the advice. "The temperatures that created the state of alarm in Britain might come as a surprise to Australians - the "heatwave" alert was triggered because temperatures are predicted to reach between 28C and 32C over two days and not dip below 15C and 18C at night," the paper said. "To put that in perspective, Sydney had 18 days with temperatures in that range in January alone. Nevertheless, the Brits are being vigilant."
Thursday: The north will be dry with highs of 24C, with the south more humid, experiencing 28C heat
Friday: The humidity will spread north with highs of 26C, but the south will swelter at 32C with heavy showers forecast
Saturday: Thunderstorms are forecast across the country, with temperatures up to 30C
The TUC said the rise in temperatures had left many workplaces unbearably hot, with many people "visibly wilting". Firms were urged to allow staff to wear shorts, vest tops or other less formal clothing, and to give employees regular breaks.
Forecaster Dan Williams said: "We would expect to get into the early 30Cs tomorrow so this is likely to be a short-lived record."
The top temperature in Wales today was 25.1C at Hawarden Airport, with highs of 22.8C and 23.2C in Scotland (Fife) and Northern Ireland (County Down) respectively.
That could climb a couple of degrees tomorrow as the so-called "Spanish plume" sweeps across the South. It can lead to warm conditions and heavy showers or thunderstorms.
But those planning beach breaks or summer weddings this weekend may be wise to pack umbrellas, with the prospect of thunder and heavy showers overnight into Saturday.
It has prompted the Met Office to issue a severe weather warning for much of the country on Saturday, with the potential for localised flooding.
Exeter-based meteorologist Mr Williams said: "We could see some heavy showers in the South West tonight moving into Wales and the west of England tomorrow."
Malcolm Bell, board member of the Devon and Cornwall Business Council, said talk of a heatwave had been a shot in the arm for tourism in the South West.
He said: "There have been health warnings and talk of 30C temperatures keeping people inside, but it has had the opposite effect down here because people have been coming to the beaches and the coastal spots for the sea breeze.
"I was down on Perranporth (a long beach near Newquay in north Cornwall) at 6pm yesterday and the place was packed.
"It can be a real draw for people to escape the heat of the city.
"Even if people don't want to go swimming, plenty are happy for a dip in the sea or to be by the coastline to cool off a bit, so I'm sure this weather is doing well for the economy down here, as you'd expect."
#heatwave survival advice: if you feel a bit hot, maybe go somewhere a bit cooler. Perhaps sit down, and consider a glass of water.— donkey_walloppa (@donkey_walloppa) July 17, 2014
#heatwave - keep cool by shaving off all body hair then stand panting at open window while naked. It's working for me.— TheBigPaul-C (@TheBigPaulC) July 17, 2014
Health warnings have already been issued, while motorists have been warned to take care as roads become sticky under the weight of increased traffic on the UK's sweltering roads.
AA spokesman Mark Spowage said: "It's going to be a hot and sticky time on the roads, literally in some places, as these temperatures can soften the road surface and make them uneven.
"Changing conditions on Saturday will bring torrential thundery showers in places.
"While they are likely to be short-lived, water will quickly run off causing localised flash flooding as well as making the roads pretty slippery.
"Keep your speed down and don't risk driving through flood water."
Public Health England said people should consider staying out of the sun during the hottest part of the day, drink plenty of fluids and wear sun cream that is at least factor 15.
It has also asked people to be aware of children and the elderly, to ensure they are not suffering because of the heat.
People should never be left in closed, parked cars, especially infants, young children or animals, a spokesman added.
Pet owners were also advised to keep their animals well-hydrated to avoid the risk of them developing heatstroke.
Forecasters said Sunday should bring fresher conditions but the south of the country was expected to remain warm into next week.