LONDON — Put a hat on. Slather on the sunscreen, and drink plenty of water.
That was the advice in Britain as the forecast this week for extreme summer heat inched up toward possibly record-breaking highs.
Meteorologists are warily eyeing the days ahead, bracing for a weekend that could come dangerously close to temperatures never experienced before in a place where umbrellas are used more as shelter from drizzling rain than as shade from the beating sun.
The highest officially recorded temperature in Britain was 38.7 degrees Celsius (101.6 Fahrenheit) on July 25, 2019, and the prospect for that ceiling to be broken looked so grim that the Royal Meteorological Society recently ventured a guess about the worst-case scenario: “40 C in the UK?”
“Temperatures in the UK have never reached 40 C since records began,” the organization said this month. (That’s 104 Fahrenheit.) “But at the end of June 2022, for the first time ever, weather forecast models started to show it as a possibility for mid-July.”
Britain’s national weather service, known as the Met Office, said on Wednesday that while some computer models were predicting temperatures could hit that 40 Celsius benchmark, more likely scenarios showed temperatures slightly lower than that, but still extremely warm.
The Met Office has issued an amber warning about the approach of extreme heat for much of England and parts of Wales. “Exceptionally” high temperatures are expected between Sunday and Tuesday before settling into cooler — or not as hot — weather for the rest of the week, the forecast says.
“We only do that when temperatures are going to be extreme, widely low- to mid-30s,” said Alex Deakin, a meteorologist with the Met Office.
Starting on Sunday, the prospect of hitting another record loomed. “We could easily get close to that, most likely on Monday,” Mr. Deakin said in a question-and-answer session on Twitter on Tuesday, as temperatures climbed toward a warmer-but-not-quite-so-scorching 30 Celsius (86 Fahrenheit) in London.
The heat will peak on Monday and Tuesday, with temperatures that could surpass 35 Celsius (95 Fahrenheit) in the southeast, but more widely will settle around 32 Celsius (89.6 Fahrenheit), forecasts say.
In London this week, shops prominently displayed hand-held battery-operated fans. The mayor activated emergency protocols to help homeless people find places to stay cool. The Met Office warned there could be disruptions of services, including water, electricity and travel, and related illnesses such as heat exhaustion. The National Health Service issued an advisory with tips on how to cope.
The Drapers Arms, a pub in North London, said it would not open on Monday and possibly other days because the forecast was unacceptable. Like other historic buildings, and many homes in Britain, the pub does not have air conditioning.
“It gets too hot in the kitchen,” said Melanie Hunt, an assistant manager. “They can’t work under those conditions. It is for the staff, especially the kitchen, but the front of house as well.”
“We have fans but I don’t think they do too much, unless you are right in front of it.”
July has already been warm in parts of Britain. Summer days in southern England typically fall in the mid-30s, although the mid- to high 30s are becoming increasingly common, depending on the region.
Sunday was the hottest day so far this year in Scotland, which hit 29.3 Celsius (84.7 Fahrenheit), and in Northern Ireland, which reached 24.3 Celsius (75.7 Fahrenheit), Mr. Deakin said in an interview on Thursday.
“We get huge swings,” he said.
Last summer, as temperatures hovered around 30 Celsius, the Met Office issued its first ever extreme heat warning, and it warned that more would come. “Although hot weather can often be seen as ‘good news’ and is enjoyed by many, it can have serious consequences,” the Met Office said at the time. “Research shows that, as a result of climate change, we are now much more likely to see prolonged spells of hot weather here in the U.K.”
“This isn’t just a typical July hot spell,” said Mr. Deakin during his online presentation this week, fielding questions from Twitter users about vacation plans, when they could expect rain (possibly the last weeks of July), and whether businesses or schools would need to be closed (it’s up to them, Mr. Deakin said).
Despite the bracing expectations, Britain may not be as bad off as some countries.
This week, temperature forecasts exceeded 104 degrees Fahrenheit in dozens of cities in eastern and southern China. Italy is in the grip of a drought, exacerbated by high temperatures, that has led to water rationing. The scorching heat reflects a global trend of increasingly frequent episodes of extreme weather driven by climate change.
“The highest temperatures experienced in the U.K. tend to occur when our weather is influenced by air masses from continental Europe or North Africa — as it will be at the weekend,” Dr. Mark McCarthy, the head of the Met Office National Climate Information Centre, said in a statement.
On Mr. Deakin’s Twitter chat, one man said he was concerned about the heat combined with high humidity in Britain, a combination that he said “will cook us.”
“It’s a different kind of heat,” Mr. Deakin agreed, referring to how it feels in hotter climates such as in Dubai, where temperatures are surpassing 38 Celsius (100 Fahrenheit) regularly this week. “That dry heat you get in the desert is easier.”
“The more moisture there is in the atmosphere, so the more humid it is, the harder it is for the body to sweat,” he explained, while warning listeners to wear a hat, apply sunscreen and drink plenty of water.