LONDON — Weeks after recording its highest-ever temperature, Britain was preparing for another unsettling stretch of hot weather, as officials said an extreme heat warning would be in place for much of the southern half of England and parts of Wales from Thursday through the weekend.
Although meteorologists predicted temperatures would be unpleasantly hot this week, they were not expected to be as extreme as those in July, when they reached above 40 degrees Celsius (104 Fahrenheit) in Britain for the first time. Because of the expected heat this week, the U.K. Health Security Agency issued a Level 3 heat-health alert for southern and central England until Sunday, and it advised more vulnerable populations to stay hydrated and to take the necessary steps to prevent their homes from overheating. Most homes in Britain lack air-conditioning.
The heat was forecast to build throughout the week, peaking on Friday and Saturday, according to the Met Office, Britain’s national weather service. Areas across central and southern England could reach up to 35 degrees Celsius (95 Fahrenheit). Other parts of England, Wales and Scotland could see the mercury rise to 29 degrees Celsius (84 Fahrenheit). Similar sizzling conditions were expected in Northern Ireland.
“What the July heat wave had was this kind of southern spike toward record-breaking temperatures, really with days of really extreme heat temperatures, where this week is more of a prolonged spell of temperatures, but not quite as hot,” Stephen Dixon, a spokesman for the Met Office, said on Tuesday by phone.
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“There are potential impacts from prolonged heat of this nature,” he said. “I think it’s important to note that nighttime temperatures for some areas in the south won’t drop below” 20 degrees Celsius (68 Fahrenheit).
Scattered thunderstorms could bring a bit of rain across the southwest and into some central areas on Sunday, Mr. Dixon said, adding that there was a chance for more rain next week.
There were also concerns that the hot weather could affect transportation, with at least one official from Britain’s National Highways advising motorists to thoroughly check their vehicles before setting out.
Pets may also struggle with the heat, another official said, adding that pet owners should look after their animals with fresh drinking water, good ventilation and shade from direct sunlight.
Last month was the driest July in England since 1935, as the country received only 35 percent of its average monthly rainfall, according to the Met Office. On Tuesday, the BBC reported that Thames Water, which serves 15 million customers in southern England, including London, was planning to temporarily ban the use of hoses to water yards and gardens and to wash vehicles. It would be the third such ban in England this year.
Also because of intensely dry conditions, fire officials in Cornwall, in southwestern England, said on Monday that there was a very high to exceptional risk of wildfire in the region and they urged residents to avoid starting bonfires and burning garden waste, as these actions could get out of control.
The heat wave across Britain in July was worsened by climate change, according to a scientific report. While tying a single heat wave to climate change requires analysis, scientists have no doubt that heat waves around the world are becoming hotter, more frequent and longer lasting. As the burning of fossil fuels causes average global temperatures to increase, the range of possible temperatures moves upward, too, making sizzling highs more likely. This means every heat wave is now made worse, to some extent, by changes in planetary chemistry caused by greenhouse-gas emissions.