Tokyo,  Japan's weather agency on Saturday said the country has just experienced its second-hottest summer on record, after seeing record-breaking temperatures.

The Japan Meteorological Agency (JMA) recently issued a report based on data from June to August, noting that the average temperature was 0.91 degrees centigrade warmer than usual, which marked the second highest after 2010 since record-keeping began in 1898.

The mercury skyrocketed especially in eastern and western Japan, and the Okinawa and Amami regions, reports Xinhua news agency citing the JMA as saying.

The city of Isesaki, north of Tokyo, reported the country's highest-ever temperature in June at 40.2 degrees, beating the previous June record of 39.8 set in 2011.

The JMA said the average sea surface temperature in waters near Japan this summer was 0.8 degrees warmer than usual, the highest figure since record-keeping began in 1982, tying with 2001 and 2016.

The rise in temperature was owing to a Pacific high-pressure system that extended mainly over waters south of Japan, and global warming may have been a factor, public broadcaster NHK reported on Saturday, citing weather officials.

Record temperatures are likely to become more frequent due to global warming, said NHK.