Western Europe sweltered through its hottest June on record last month, as "extreme" temperatures blasted the region in punishing back-to-back heatwaves, the EU climate monitor Copernicus said on Wednesday.

Globally, this past June was the third warmest on record, continuing a blistering heat streak in recent years as the planet warms as a result of humanity's emissions of greenhouse gases.

The previous hottest June was in 2024 and the second hottest was in 2023, the Copernicus Climate Change Service said.

Sweltering extremes were particularly pronounced in Europe, which is warming several times faster than the global average. Several countries recorded surface temperatures above 40 degrees Celsius, with heat of up to 46 degrees in Spain and Portugal.

Millions of people were exposed to high heat stress across parts of the continent as daily average temperatures in western Europe climbed to levels rarely seen before -- and never so early in the summer.

Samantha Burgess, the EU monitor's Strategic Lead for Climate, said the impact of the heatwaves in Europe was "exceptional", intensified by record sea surface temperatures in the western Mediterranean – which hit an all-time daily maximum in June.

The two heatwaves – from June 17 to 22, and again from June 30 to July 2 – were linked to heat domes trapping warm air over affected regions, prolonging the stifling weather and worsening pollution and wildfire conditions.

Portugal, Spain, France, Italy and much of the Balkans saw some of the hottest "feels-like" temperatures, which measure the impact on the human body by taking into account factors like humidity.

Maximum feels-like temperatures north of Lisbon hit 48 degrees, around seven degrees above average and associated with "extreme heat stress", said Copernicus.

Sea surface temperatures across the western Mediterranean were "exceptionally high", some five degrees above average in some areas, with temperatures surging to a record 27 degrees on June 30.

The higher water temperatures reduced nighttime air cooling along the coasts, contributed to higher humidity, and harmed marine life, Copernicus said.

Dangerous heat blanketed parts of the United States, while in China, 102 weather stations logged the hottest-ever June day, with some measuring temperatures above 40 degrees, according to state media.

Devastating wildfires blazed across parts of Canada and southern Europe, while deadly flooding swept areas of South Africa, China and Pakistan. (AFP)