Last month was so hot it set a new record for the planet, marking the warmest May over land and water since record-keeping began in 1880, US authorities said Monday.
The combined average temperature across the globe was 59.93°F (15.54°C), or 1.33°F (0.74°C) above the 20th century average, said the National Oceanic and Atmospheric Administration.
The previous record for May was set in 2010.
"The majority of the world experienced warmer-than-average monthly temperatures, with record warmth across eastern Kazakhstan, parts of Indonesia, and central and northwestern Australia," NOAA said.
The findings are part of an ongoing trend of rising global warmth.
Each and every May over the past 39 years has been hotter than the 20th century average, according to NOAA.
April was also historically hot across the globe, and tied with 2010 for the highest average temperature since 1880, NOAA said.
The last time global May temperatures fell below the 20th century average was in 1976, the agency said.