Japan had its second-hottest September since records began with some regions the warmest yet, the weather agency said, in a year likely to become the warmest in human history.
Across the archipelago the month's average temperature was 2.52 degrees Celsius higher than usual, the Japan Meteorological Agency said Tuesday.
This was "the second highest figure since the start of the statistics in 1898, after last year's high", a statement said.
But some regions, including eastern and western parts of mainland Japan, logged the highest ever average temperatures for September since comparable data began available in 1946, the agency added.
The subtropical jet stream's peculiar northward movement, as well as the Pacific high pressure system that extended towards Japan, made it easier for warm air to shroud the archipelago, the agency said.
"The temperature of the ocean surface near Japan was also markedly high, which possibly contributed to high temperatures on the ground," it added, citing the "long-term effect of global warming" as well.
The average global temperature at the Earth's surface was 16.82C in August, according to the EU's climate monitor Copernicus, which draws on billions of measurements from satellites, ships, aircraft and weather stations.
June and August global temperatures broke through the level of 1.5C above the pre-industrial average -- a key threshold for limiting the worst effects of climate change.
Human-caused greenhouse gas emissions are warming the planet, raising the likelihood and intensity of climate disasters such as droughts, fires and floods.
