Monday, July 3, was the world's hottest day ever recorded, according to data from the U.S. National Centers for Environmental Prediction.

The average global temperature hit 17.01 degrees Celsius, beating the August 2016 record of 16.92 degrees Celsius as heatwaves left millions around the globe sweltering.

In China, an enduring heatwave continues with temperatures above 35 degrees Celsius, while the southern U.S. has been suffering under an intense heat dome in recent weeks. North Africa has seen temperatures near 50 degrees.

And even Antarctica, currently in its winter, registered unusually high temperatures. Ukraine's Vernadsky Research Base in Antartica's Argentine Islands recently broke its July temperature record with 8.7 degrees.

"This is not a milestone we should be celebrating," said climate scientist Friederike Otto of the Grantham Institute for Climate Change and the Environment at Britain's Imperial College London.

"It's a death sentence for people and ecosystems."

Scientists said climate change, combined with an emerging El Niño pattern, were responsible.

"Unfortunately, it promises to only be the first in a series of new records set this year as increasing emissions of [carbon dioxide] and greenhouse gases coupled with a growing El Niño event push temperatures to new highs," said Zeke Hausfather, a research scientist at Berkeley Earth.

Meanwhile in Britain, last month was the hottest June on record, the country's national weather service said, warning that human-induced climate change was making such temperature records increasingly likely.

Record heatwaves have become a worldwide pattern, as scientists warn that efforts to halt a rise in temperatures are falling short of what is needed to avert the most catastrophic effects of global warming.

"All the numbers are suggesting that we're going in the wrong direction when it comes to the heat, the intensity of the heat and how prolonged it is," said UK Met Office meteorologist Clare Nasir.

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