September 2025 was the third warmest on record behind September 2023 and 2024, according to the European Union’s Copernicus Climate Change Service (C3S). The month was notable due to the exceptionally high global average surface air temperature of 16.11°C, which was 0.66°C higher than the average from 1991 to 2020 and 1.47°C higher than the pre-industrial average (1850–1900). The twelve-month worldwide average temperature from October 2024 to September 2025 was 1.51°C higher than pre-industrial values, which is even more alarming and underscores the ongoing human-induced climate change.

Despite La Niña-like circumstances in the equatorial Pacific, a natural trend usually associated with global cooling, this extraordinary warming took place. The fact that global temperatures remained steady during this cooler period indicates that the impact of greenhouse gas-induced background warming on the planet’s climate is becoming more profound.

Record Warmth in Oceans and Atmosphere

In September 2025, the waters and atmosphere both mirrored the ongoing trend of heat.

• September 2025 was the third warmest on record, with an average worldwide sea surface temperature (SST) of 20.72°C, about 0.20°C warmer than 2023, the warmest year on record.
• Significantly above-average temperatures were also recorded in the Norwegian Sea, Mediterranean Sea, and Kara Sea. At the same time, the North Pacific Ocean was especially unusual, with record-high SSTs in multiple areas.
• The heat was most severe in the western and central Mediterranean, significantly upsetting marine ecosystems and increasing evaporation rates.

In many regions of the world, catastrophic weather events—especially intense rain and flooding—were exacerbated by these warmer water temperatures. Excessive rainfall occurred in sections of Italy, Scandinavia, Finland, coastal Croatia, eastern Spain, and the northwest and central regions of Europe. The rains caused significant flooding in several of these areas, upsetting infrastructure and populations.

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Global Impacts: From Floods to Shifting Climate Patterns

The September 2025 weather disruptions caused by warmth were not limited to Europe. There were also notable climatic anomalies on other continents:

• Rainfall in North America was more than usual in Alaska, northwest Mexico, and the southwestern and central United States.
• While northern Africa, especially the Horn of Africa, was wetter than typical, South America saw excess precipitation in Brazil, Argentina, and Chile.
• In Asia, Pakistan, southern Arabia, central Asia, eastern China, and northwest India all had more rainfall.

There is no indication that the ongoing global warming trend from 2023 to 2025 will stop. January was the warmest month on record in 2025 alone; the third-warmest months were February, June, July, August, and September, while the second-warmest months were March through May. This pattern makes it abundantly evident that natural climate cycles, such as El Niño or La Niña, are no longer the primary causes of changes in global temperatures. Instead, human-caused greenhouse gas emissions are now the primary factor influencing the course of the Earth’s climate.

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