According to NASA's monthly analysis, last month was the second hottest May in 137 years of modern record-keeping of average global temperatures.
May 2017 was 0.88 degrees Celsius cooler than the mean May temperature from 1951 to 1980.
Global temperature patterns indicate that around the Antarctic, temperatures rose up to 5°C above normal. Africa and most of North America, too, experienced above average temperatures.
How May 2017 compares to previous May months
2016 witnessed the hottest May on record, at 0.93°C warmer than the May mean temperature. May 2017 was only 0.05°C cooler than last year. Last month was only 0.01°C warmer than the third warmest May, which occurred in 2014.
The temperature analysis process
The monthly analysis is conducted by NASA's Goddard Institute for Space Studies based on publicly available data.
This data is recorded by around 6,300 meteorological stations around the world, ship-and-buoy based instruments measuring sea surface temperature, and Antarctic research stations.
The modern global temperature record begins from 1880, as previous observations did not cover enough of the planet.