Last month was the hottest August on record for global average temperatures over land and ocean surfaces, the US National Oceanic and Atmospheric Administration said on Thursday.
If the trend continues, 2014 could set new records for planet-wide heat, a development that would raise new alarm over the pace of global warming and the burning of fossil fuels.
The month's temperature was 1.35 degrees Fahrenheit above the 20th century average, the agency said in its monthly climate report.
"It was the largest departure from average of any month on record," said Jake Crouch, a climate scientist at NOAA, noting that record-keeping began in 1880.
The month's average land and ocean surface temperature was 61.45 Fahrenheit (16.35 Celsius). The 20th century average for August is 60.1°F (15.6°C).
The period of January to August was also the third warmest on record, said the report.
"If we continue a consistent departure from average for the rest of 2014, we will edge out 2010 for the warmest year on record," Crouch told reporters.
"Another way to think of that, if the next four months -- September through December -- if each of those months rank among the five warmest on record, 2014 will be the warmest year on record for the globe."
Most of the global oceans were much warmer than average last month, he added.
On land, temperatures across the United States were near average, while parts of Europe, central Asia and Australia were near average to slightly cooler than average.