July 21 was the hottest day ever registered globally, according to preliminary data published Tuesday by the EU's climate monitor.
The Copernicus Climate Change Service (C3S) said the global average surface air temperature of 17.09 degrees Celsius (62.7 degrees Fahrenheit) on Sunday was the warmest in their record books, which go back to 1940.
It comes as heatwaves and wildfires ravage swathes of Europe and the United States.
"The Earth has just experienced its warmest day," the monitor said in a statement.
The new daily high was 0.01 degree Celsius above the previous record temperature of 17.08 registered on July 6, 2023.
"On July 21st, C3S recorded a new record for the daily global mean temperature," C3S director Carlo Buontempo said in a statement.
"We are now in truly uncharted territory and as the climate keeps warming, we are bound to see new records being broken in future months and years," he said.
Though just a tiny rise above the previous record, what was "truly staggering" was the streak of unprecedented global heat recorded over the past 13 months, Buontempo added.
Every month since June 2023 has eclipsed its own temperature record compared to the same month in previous years.
Copernicus said in this context, and at the peak of the northern hemisphere summer, it was not "completely unexpected" that this new daily high would be breached.
It could be eclipsed by the soaring heat experienced earlier this week, the monitor said, pointing to a streak of record-breaking days that occurred in July and August 2023.
Global temperatures were expected to peak and drop soon though there could be further fluctuations in coming weeks, Copernicus said.
- Heat and fire -
Climate change is causing longer, stronger and more frequent extreme weather events like heatwaves and floods, and this year has been marked by major disasters across the globe.
Deadly heatwaves have already hit North America, Mexico, India and Thailand this year, to name a few, while flooding has devastated parts of East Africa, China and Brazil.
Wildfires are torching a path across southern and eastern Europe and in Canada and the United States as prolonged scorching temperatures in parts of the northern hemisphere make conditions tinder dry.
The burning of fossil fuels is the primary driver of global warming but emissions of heat-trapping greenhouse gases keep rising, despite international efforts to switch to clean energy and slow rising temperatures.
2023 was the hottest year on record and 2024 could follow in step considering the "sufficiently warm" temperatures experienced to date, Copernicus said.
But it was "too early to predict with confidence" which would be hotter between the years, it added.
