Japan and South Korea endure record-breaking summer heat fueled by climate change - August 2025

Unusual temperatures: 

• Japan experienced its hottest June on record, with the national average temperature 2.3°C (4.2°F) above normal, according to the Japan Meteorological Agency.

• The heat wave intensified in July 2025, which became the hottest in the country’s 127-year record. The average temperature ended the month 2.9°C (5.2°F) above the 1991-2020 average.

• South Korea recorded its second-hottest July since records began in 1973, with an average temperature of 27.1°C (80.7°F).

• According to the Korea Meteorological Administration, Seoul, South Korea, set a new July record for the most ‘tropical nights’ — tropical nights refers to when overnight temperatures remain above 25°C (77°F) between 6:01 p.m. and 9 a.m. the next day.

Climate influence: Daily average temperatures reached a CSI level 5 across Japan and South Korea from mid-June to early August. Several cities saw over a month of CSI 5. A CSI 5 indicates that human-caused climate change made this event at least five times more likely, signaling an exceptional climate change event. 

“This summer’s heat in Japan and South Korea is not a fluke — it’s the fingerprint of climate change, made worse by continued fossil fuel use,” said Zachary Labe, a climate scientist at Climate Central. “Children, older adults, and people with pre-existing health conditions are the most at risk when heat waves like this strike. We know that burning coal, oil, and gas is driving these extremes.”

Temperature and CSI Data (June 15 - August 4, 2025 #

See this event on the Climate Shift Index map