Global air and sea temperatures set new records during the past summer.

Omissions

• Global air temperature records were set in August 2026 (joint warmest August and joint hottest month on record), but June 2026 was only the second-warmest June and July 2026 the joint second-warmest July, so the summer as a whole was not necessarily the warmest summer on record for surface air temperature.
• The record-breaking ocean warmth was continuous across all three summer months, whereas the air-temperature record was concentrated in August.
• All figures come from the Copernicus ERA5 reanalysis; monthly bulletins were published in July, August and September 2026 and the September bulletin on 12 October 2026, i.e. all before the 21 October 2026 session date.

Sources

• PrimaryCopernicus Climate Change Service (C3S) — 'August was the world's joint hottest month on record'"The global-average surface air temperature in August 2026 was 16.96°C, 0.85°C above the 1991–2020 average, making it the warmest August globally" (and the world's joint hottest month on record).
• PrimaryCopernicus Climate Change Service — Surface air temperature for August 2026"The average sea surface temperature (SST) across the extra-polar ocean (60°S-60°N) was 21.07°C in August 2026, the highest value recorded for" August.
• PrimaryCopernicus Climate Change Service — June 2026 bulletin"June 2026 was the second-warmest June globally in the ERA5 dataset, with an average surface air temperature of 16.54°C, 0.56°C above the 1991-" 2020 average.
• PrimaryCopernicus Marine Service — press release on first half of 2026"Record global sea surface temperatures of 21.0°C made June 2026 the warmest June ever observed."
• PrimaryCopernicus Climate Change Service — July 2026 bulletin"July 2026 was the joint-second warmest July* globally in the ERA5 dataset, tied with July 2024 and behind the record set in July 2023"; the bulletin also reports the "Highest July global ocean surface temperatures".
• PrimaryCopernicus Climate Change Service — Climate Bulletins (September 2026)"The global-average surface air temperature in September 2026 was 16.27°C, 0.82°C above the 1991–2020 average" — the second-warmest September on record, confirming that the record warmth of August 2026 did not persist at record level into the autumn.