Global ocean surface temperatures in September 2026 ran 1.10 degrees Celsius (1.98 degrees Fahrenheit) above the long-term average, a new monthly record and the fourth straight month in which the world’s seas have broken the mark. The margin over August was thin, just 0.02 degrees Celsius, but the direction has not changed since the streak began. NOAA’s National Centers for Environmental Information published the figures on October 9.
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The ocean number sits inside a month that was otherwise a near miss for the planet as a whole, with land and sea together finishing as the second-warmest September rather than the warmest. The gap between the two results shows how much of the recent record-setting is being driven by the water.
NOAA’s September ocean reading
According to the NCEI global climate summary for September, sea surface temperatures were 1.10 degrees Celsius above average, the highest departure recorded for any month in the dataset. The reading beat the August 2026 record by 0.04 degrees Fahrenheit, which makes September the fourth consecutive monthly ocean record. A Meteored report on the NOAA release reached the same figures and described the ocean result as the standout of the month.
Records of this kind are set by small increments, and the 0.02-degree gap is a useful reminder of how the series behaves. Ocean heat changes slowly because water holds far more energy than air, so a month that edges past its predecessor is usually the continuation of a trend that has been building for a long time. Four such edges in a row mean the baseline itself is climbing, month after month, rather than a single hot spell pushing one reading higher. For coastal communities, fisheries and anyone who lives in the path of tropical storms, a warmer sea surface also means more energy available to feed storms and more stress on marine ecosystems, which is why the ocean series draws such close attention each month.
El Niño warming in the equatorial Pacific
NCEI attributes much of the ocean warmth to El Niño, noting some of the warmest waters in the central and eastern tropical Pacific. NOAA’s Climate Prediction Center, in its October 8 El Niño advisory, said a strong-to-very strong event is likely through January to March 2027 with a probability above 83 percent. Sea surface temperatures exceeded 4.0 degrees Celsius above average in parts of the eastern equatorial Pacific, and the Niño-3.4 region stood at 2.1 degrees Celsius above average.
The Met Office in the United Kingdom has gone further on the historical comparison. Meteored’s account of the Met Office statement says central equatorial Pacific temperatures have already exceeded those of any previous El Niño in the observational record, and that the event has not yet peaked. Professor Adam Scaife, the Met Office’s head of long-range prediction, said forecasters had been signalling for months that the event would be unprecedented.
The Met Office’s Dr. Nick Dunstone drew out what comes next. Large El Niños release stored ocean heat into the atmosphere, he said, with the effect typically appearing the year after the winter peak, and “2027 is very likely to replace 2024 as the warmest year on record.” Meteored’s report adds that the Met Office expects 2027 to temporarily exceed 1.5 degrees Celsius above pre-industrial levels, while stressing that long-term human-caused warming is also at work and that scientists will watch how the two interact. The Climate Prediction Center, for its part, gives a 54 percent chance for September to November and 83 percent for October to December that the event will exceed the strength of any El Niño since 1950.
Air temperatures, sea ice and storms in the same report
Land and ocean combined were slightly less dramatic than the ocean alone. NCEI ranked September 2026 as the second-warmest September in records that start in 1850, behind 2023, at 1.33 degrees Celsius (2.39 degrees Fahrenheit) above the 20th-century average. Meteored puts the gap to the 2023 record at 0.07 degrees Celsius. It was the 51st consecutive September above that average, and the Arctic, North America and Asia each recorded their warmest September on record.
Land surfaces averaged 1.83 degrees Celsius above average, the third-highest September in the 177-year land record. Global sea ice extent was the third smallest for September in the 48-year satellite record, about 800,000 square miles below the 1991 to 2020 average. Storm tallies were also unusual: the eastern North Pacific set September records for hurricanes and major hurricanes, while the Atlantic had no hurricanes before October, a first in the satellite era.
Where 2026 stands for the year
January through September 2026 ranked as the second-warmest such period on record, behind 2024, according to NCEI. The agency says 2026 is very likely to finish among the five warmest years, with second place the most probable outcome. The next monthly report will extend the ocean series to a possible fifth record, and the NCEI monthly report archive is where each new edition appears.
Whether October extends the streak depends largely on how fast the Pacific event keeps strengthening, since the Climate Prediction Center’s next update is due on November 12. Until then, the September figures stand as the most recent word from NOAA on how warm the world’s oceans have become.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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