NOAA puts September's global sea surface temperature 1.10°C above its 20th-century average. That beats August's record, but only by 0.02°C, with El Niño conditions persisting in the Pacific.
The US National Oceanic and Atmospheric Administration published its September global climate report on 9 October. It says the global ocean surface averaged 1.10°C above its 20th-century average. That is the largest departure for any month in its record, which begins in 1850. The previous record, 1.08°C, was set only a month earlier, in August 2026.12
NOAA also reports that the ocean departure has set a new high for its time of year for four months in a row. In its monthly series, June reached 0.99°C, July 1.02°C, August 1.08°C and September 1.10°C. Before August, the highest month on record was 1.03°C, in January and February 2024.2
Looking only at Septembers shows the long-run shift. Until 2023, no September had been more than 0.76°C above the 20th-century average. September 2023 reached 1.02°C. September 2026 is 0.08°C higher again.2
Combining land and ocean, NOAA ranks September 2026 as the second-warmest September, at 1.33°C above average and 0.07°C behind September 2023. All ten of the warmest Septembers have come since 2015. The land surface alone was third-warmest for the month. NOAA reports that September was the warmest on record for the Arctic region, North America and Asia. January to September 2026 was the second warmest such period, behind 2024.1
Context. NOAA attributes record warmth in the central and eastern tropical Pacific to persistent El Niño conditions.1 Copernicus reported record daily sea surface temperatures for the time of year in June, as El Niño began.3 On 21 September a daily measure in the equatorial Pacific was 3.08°C above its 1991–2020 average, above any recorded El Niño. NOAA has not ranked the event as the strongest, because its official measure uses three-month averages.4
How much of the record is El Niño and how much is the long-term warming trend cannot be read off these figures. Whether ocean warmth keeps rising also depends on when El Niño peaks, which NOAA scientists expect within months.4 Other datasets use different baselines, areas and methods, and may rank these months differently.