The World Meteorological Organization (WMO) says Earth just had its hottest summer ever in the Northern Hemisphere.
Summer ends on September 22 this year in the world's northern half.
Last month was the hottest August ever recorded with modern equipment since 1979.
It was also the second hottest month ever measured, behind only July 2023.
The WMO and the European climate service Copernicus made the announcement Wednesday.
August was about 1.5 degrees Celsius warmer than pre-industrial averages.
That is the limit world leaders have said the world must not pass.
Scientists, however, are more concerned about temperature increases over many years and not just a few months.
So far, Copernicus said 2023 has been the second hottest year that it has recorded, behind only 2016.
But the University of Maine's Climate Reanalyzer, a website, reported that daily September temperatures are higher than those recorded for the same period in earlier years.
The WMO also said the world's oceans were the hottest ever recorded at nearly 21 degrees Celsius.
Water covers more than 70 percent of the Earth's surface.
"The dog days of summer are not just barking, they are biting," United Nations Secretary-General Antonio Guterres said in a statement.
"Dog days of summer" is an expression used to describe the time of hot and humid weather during the summer.
The expression might have come from ancient Greece when extreme heat was said to drive both dogs and humans insane.
Scientists blame the heat on the burning of coal, oil and natural gas and the added influence from El Nino for the warming climate.
El Nino is a temporary warming of the southern Pacific Ocean that affects weather worldwide.
The weather event changes weather around the world and even more so in its second year.
Climatologist Andrew Weaver was not surprised by the numbers.
He said governments have not taken global warming seriously enough.
He expressed concern that the public will forget the issue when temperatures fall again.
"It's time for global leaders to start telling the truth," said Weaver who is a professor at the School of Earth and Ocean Sciences at the University of Victoria in Canada.
"We will not limit warming to 1.5 Celsius; we will not limit warming to 2.0 Celsius. It's all hands on deck now to prevent 3.0 Celsius global warming."
Copernicus Climate Change Service Director Carlo Buontempo said the high temperatures were "not only new extremes" but continuing "record-breaking conditions."
While the world's air and oceans were setting records for heat, Antarctica continued to set records for low amounts of sea ice, the WMO, the United Nations weather agency, said.
"Antarctic sea ice extent was literally off the charts, and the global sea surface temperature was once again at a new record," WMO's secretary-general, Petteri Taalas, said in a statement.
Taalas added, "It is worth noting that this is happening BEFORE we see the full warming impact of the El Nino event."
I'm Dan Friedell.