September 2025 Temperature Update

The following is a summary of global temperature conditions in Berkeley Earth’s analysis of September 2025.

• September 2025 was the third warmest September on record behind 2023 and 2024, with a global average of 1.48 ± 0.15 °C (2.67 ± 0.26 °F) above the 1850-1900 average.
• Land temperatures averaged 2.02 ± 0.28 °C (3.64 ± 0.50 °F) above the 1850-1900 average, ranking as the 3rd warmest September for terrestrial regions.
• Ocean temperatures were 1.01 ± 0.13 °C (1.82 ± 0.23 °F) above the 1850-1900 average, making it the third warmest September for ocean surfaces.
• Officially still ENSO-neutral, but with cooling that suggests a return to La Niña is likely to occur imminently.
• 4.1 % of Earth’s surface experienced a record high September monthly average (2.8% and 4.8% of land and ocean surfaces respectively).
• 2025 now has a 93% likelihood to be the third warmest year on record and a 3% chance to have an annual average above 1.5 °C.

Global Summary

September 2025 was the third warmest September on record, with a monthly global average of 1.48 ± 0.15 °C (2.67 ± 0.26 °F) above the 1850-1900 average. Along with 2023 and 2034, the last three Septembers have been sharply warmer than all measured Septembers 1850 to 2022. If not for the extreme warmth in 2023 and 2024, 2025 would have been considered a sharp step up from the previous Septembers.

Month-to-month temperatures continue to tick upward markedly in September 2025, bouncing off the recent lows and rising slightly above the long-term trend line. However, conditions remain cooler than during the bulk of 2023 and 2024.

September 2025 was cooler than 2023 and 2024, but significantly warmer ( by ~ 0.25 °C) than any September prior to 2023. Temperatures were nominally slightly below 1.5 °C, but within uncertainties of that threshold.

The 12-month moving average remains well above the long-term trend line. However, it appears clear that the short-term natural variability contributing to anomalous warmth in 2023 & 2024 has peaked, and we expect the 12-month average will soon return towards the trend line. Short-term variability is an inherent part of the weather and climate and is to be expected even alongside persistent long-term global warming.

Spatial Variation

In September 2025, elevated temperatures were prevalent across North America, Scandinavia, North East Asia, the Arctic Ocean, North Pacific Ocean, and around much of Antarctica. Cooler temperatures were present in the northern North Atlantic.

4.1 % of Earth’s surface experienced a record high September monthly average (2.8% and 4.8% of land and ocean surfaces respectively), with record warmth in parts of the North Pacific Ocean, Canada, Western Africa, Scandinavia, and Indonesia/Papua New Guinea.

Over land regions, September 2025 was the third warmest September since 1850, with a terrestrial average of 2.02 ± 0.28 °C (3.64 ± 0.50 °F) above the 1850 to 1900 average, on par with the long term trend.

Average ocean temperatures in September 2025 were equal to 1.01 ± 0.13 °C (1.82 ± 0.23 °F) above the 1850 to 1900 average. This was the third warmest September (again behind 2023 and 2024), and close to the long-term trend line.

Continuing NOAA Data Problems

The current monthly report is prepared using data available to Berkeley Earth as of mid-October 2025. However, we are working around problems with NOAA input data. Since late August 2025, core NOAA climate archives, including the Global Summary of the Day, Global Historical Climatology Network – Daily, and Global Historical Climatology Network – Monthly (GHCN-M), have been broken or incomplete. Because Berkeley Earth draws from multiple data sources, we are resistant to these problems but not entirely immune to them.

In the case of GHCN-M, which is NOAA’s flagship climate monitoring platform, the defects are strongly clustered with NOAA failing to report nearly all observations from China, Kazakhstan, the Philippines, Spain, and certain other areas. These weather stations continue to be operated by their local meteorological agencies, but their observations have not been captured by NOAA aggregation services.

Drawing on alternative data sources allows us to fill some of the gaps created by missing NOAA data aggregation services, but we still have less data than we would ordinarily expect. As a result, the maps have unusual gaps in Africa and the land-average uncertainty has temporarily spiked to a ~50 year high.

It is normal to encounter sporadic delays in weather station reporting, and as a result, it is also normal to revise the analysis as more data becomes available. However, the current disruption resulting from the loss of NOAA services is large than the typical delays and more spatially clustered. We expect the problems with NOAA data aggregation will ultimately be temporary, as the underlying weather stations still exist, and it is simply a matter of getting suitable access. Future revisions, Incorporating additional data, should reduce the uncertainty to a normal level.

ENSO Conditions

We now calculate almost no chance that 2025 will be the warmest year on record. There is a small chance (7%) that warming over the next 3 months is sufficient to lift 2025 to be the second warmest year on record, but it is much more likely that 2025 will become the 3rd warmest year (behind 2023 and 2024). Furthermore, there is a 3% chance that global average temperature anomalies for 2025 exceed the 1.5 C (2.7 °F) benchmark above the 1850-1900 average.

Estimated Probability of 2025 annual average final rankings:

• 1^st – < 1%
• 2^nd – 7%
• 3^rd – 92.9%
• 4^th or lower – < 1%