A temperature of 54.4C – or 129.9F – has been recorded in Death Valley, California, in what some extreme weather watchers believe could be the hottest reading ever reliably recorded on the planet.
The United States National Weather Service’s automated weather station at Furnace Creek near the border with Nevada hit the extreme high at 3:41 pm on Sunday afternoon, a statement said.
It comes amid a heatwave on the US’s west coast, where temperatures are forecast to rise further this week.
The scorching conditions have led to two days of blackouts in California after a power plant malfunctioned on Saturday.
“It’s oppressive heat and it’s in your face,” Brandi Stewart, who works at Death Valley National Park, told the BBC.
Ms Stewart has lived and worked at the national park on and off for five years. She spends a lot of her time indoors in August because it’s simply too uncomfortable to be outside.
“When you walk outside it’s like being hit in the face with a bunch of hairdryers,” she said. “You feel the heat and it’s like walking into an oven and the heat is just all around you.”
Sunday’s reading was recorded in Furnace Creek in Death Valley.
Before this, the highest temperature reliably recorded on Earth was 129.2F (54C) – also in Death Valley in 2013.
A higher reading of 134F, or 56.6C a century earlier, also in Death Valley, is disputed. It is believed by some modern weather experts to have been erroneous, along with several other searing temperatures recorded that summer.
According to a 2016 analysis from weather historian Christopher Burt, other temperatures in the region recorded in 1913 do not corroborate the Death Valley reading.
Another record temperature for the planet – 131F, or 55C – was recorded in Tunisia in 1931, but Mr Burt said this reading, as well as others recorded in Africa during the colonial era, had “serious credibility issues”.
The current heatwave stretches from Arizona in the south-west, up the coast to Washington State in the north-west.
It is expected to hit its peak on Monday and Tuesday before temperatures start to drop later in the week. However, the sweltering heat will continue for at least another 10 days.
As temperatures soared in California, a large “firenado” was observed on Saturday in Lassen County.
California’s Independent System Operator (CISO), which manages the state’s power, has declared a Stage 3 Emergency, meaning “when demand [for electricity] begins to outpace supply”.
Because so much of the region’s power relies on solar and wind energy, and because people use their electricity for air conditioning, during heatwaves the power grid becomes strained and is at risk of completely malfunctioning.
In order to manage the state’s demand for power and prevent a complete shutdown, officials are using scheduled rolling blackouts to control and conserve energy.
However, extreme heat can also exacerbate pre-existing health conditions, including respiratory diseases, heart conditions and kidney disorders, the World Health Organization (WHO) says.
It can affect infrastructure, too. As well as straining power grids and causing blackouts, extreme heat can ground planes, melt roads, and cause the inside of cars to overheat to dangerous levels.
Heatwaves can also have a severe impact on agriculture – either by causing vegetables to wilt and die or by encouraging the spread of plant diseases.