Tuesday was the hottest day ever recorded as the global average temperature leaped to a record high for the second day in a row, according to preliminary readings by US meteorologists published Wednesday.

The average daily air temperature on the Earth's surface reached 17.18 degrees Celsius (62.92 Fahrenheit), according to data compiled by an organisation attached to the US National Oceanic and Atmospheric Administration (NOAA).

That far outstripped even the previous day's record measurement, a fresh sign of the impact of climate change driven by the burning of fossil fuels.

The global average temperature reached 17 degrees Celsius for the first time on Monday, according to data from NOAA's National Centers for Environmental Prediction, whose records go back to 1979.

That topped the previous daily record of 16.92 Celsius dating to July 24, 2022.

For comparison, the world's average air temperature, which fluctuates between 12 Celsius and just under 17 Celsius on any given day over the year, averaged 16.2 degrees at the beginning of July from 1979 to 2000.

This reported record has yet to be corroborated by other measurements, but could be broken again as the northern hemisphere's summer begins.

The EU climate monitoring unit Copernicus confirmed in a statement to AFP on Wednesday that Monday had been the hottest day in its dataset going back to 1940. It could not yet confirm the data for Tuesday.

The average global temperature typically continues to rise until the end of July or early August.

Even last month, average global temperatures were the warmest Copernicus had ever recorded for the start of June.

Temperatures are likely to rise even further above historical averages over the next year with the onset of an El Nino weather phenomenon in the Pacific Ocean, which the World Meteorological Organization confirmed on Monday is now underway.

In addition, human activity -- mainly the burning of fossil fuels -- is continuing to emit roughly 40 billion tonnes of planet-warming CO2 into the atmosphere every year.