Greta Thunberg Warns 'Heat Wave Is Just Getting Started' Amid Record Temperatures

As dangerously high temperatures were reported across parts of the U.S. and in Canada, which saw a new record high on Sunday, environmental activist Greta Thunberg warned the "heat-wave is just getting started."

Thunberg tweeted Monday: "'Highest temperature ever recorded in the planet north of 50N latitude also shattered (44.4C from July 1941)'—@extremetemps.

"Heat records are usually broken by decimals, like a tenth of a degree. And not in June. This heat-wave is just getting started. #FaceTheClimateEmergency." The 18-year-old activist also shared a tweet from meteorologist Scott Duncan noting the latest record temperature in Canada.

According to a tweet Sunday from ECCC Weather British Columbia, Canada's official weather and climate source, the country's "all time maximum high" temperature was recorded Sunday in Lytton, a village in the Canadian province of British Columbia.

The tweet noted: "Lytton's official high temperature today June 27, 2021 is 46.6 C. Lytton BC now holds the record for Canada's all time maximum high. The previous record was 45.0 C set on July 5, 1937 at Yellow Grass, and Midale, SK [Saskatchewan]."

Meteorologist Duncan tweeted: "It is only June. Annual highest temperature is normally in late July!"

Thunberg's latest warning comes amid a "very dangerous heat wave" taking place across the western and northwest regions of the U.S.

In a tweet Monday, the National Weather Service (NWS) said "numerous daily high records" were broken over the past weekend. Temperatures ranged from 109 F to 115 F in parts of Washington, Oregon and California on Sunday, the NWS said.

The NSW issued excessive heat warnings for nearly all of Washington and Oregon, as well as for several parts of California, Nevada and Idaho.

An excessive heat warning is issued "within 12 hours of the onset of extremely dangerous heat conditions," the NWS explains.

"The general rule of thumb for this warning is when the maximum heat index temperature is expected to be 105 [F] or higher for at least 2 days and night time air temperatures will not drop below 75 degrees.," the NWS warns. "However, these criteria vary across the country [...] If you don't take precautions immediately when conditions are extreme, you may become seriously ill or even die."

According to several international science academies, rising temperatures form part of the "strong evidence" that global warming is occurring.

The NASA website states: "Multiple studies published in peer-reviewed scientific journals show that 97 percent or more of actively publishing climate scientists agree: Climate-warming trends over the past century are extremely likely due to human activities."

In a 2005 joint statement, several academies, including the National Academy of Sciences in the U.S. and the Royal Society of Canada, said: "Climate change is real. There will always be uncertainty in understanding a system as complex as the world's climate. However there is now strong evidence that significant global warming is occurring.

"The evidence comes from direct measurements of rising surface air temperatures and subsurface ocean temperatures and from phenomena such as increases in average global sea levels, retreating glaciers, and changes to many physical and biological systems," the statement said.