September 2025: the 3rd warmest globally, but the 6th coolest since the beginning of the century in mainland Portugal

Global

According to Copernicus Climate Change Service (C3S) data, September 2025 was the 3rd warmest September on record globally, with an average surface air temperature of 16.11°C, which is +0.66°C above the 1991–2020 climate normal for the month. It was -0.27°C cooler than the record-warm September of 2023 and only -0.07°C cooler than September 2024. Compared to the estimated 1850–1900 pre-industrial average, September 2025 was +1.47°C warmer. Over the recent 12-month period, from October 2024 to September 2025, the global mean temperature was +0.63°C above the 1991–2020 average and +1.51°C above pre-industrial levels.

Europe

Copernicus Climate Change Services (C3S) analysis reported that the average temperature over European land for September 2025 corresponded to 15.95°C, +1.23°C above the 1991-2020 average for September, ranking 5th highest on record for the month.

Warmer-than-average temperatures were seen over Iceland, central and eastern Spain, Fennoscandia and in most of the eastern half of Europe. The most pronounced anomalies were recorded over northern Fennoscandia, in a region stretching straight southward from Finland, over most of the Baltic states, Belarus and western Ukraine, as well as over parts of Croatia, Serbia, Montenegro and Albania. Ireland, the United Kingdom, France, northern Portugal and northwestern Spain experienced slightly cooler-than-average temperatures, with most locations seeing anomalies that were less than one degree below average.

Mainland Portugal

September 2025 was classified as cold in terms of air temperature and dry in terms of precipitation.

Air Temperature

It was the 6th coldest September since 2000, with an average air temperature of 20.10°C, -0.41°C below the 1991–2020 normal.

• Maximum air temperature: the average maximum temperature was 26.99°C, with an anomaly of +0.18°C above the normal 1991-2020.
• Minimum air temperature: the 3rd lowest value since 2000, with an average minimum temperature of 13.20°C, -0.99°C below the 1991–2020 average.
• During the month, a warmer period occurred between 14 and 19 September, when over 70% of IPMA stations recorded maximum temperatures above 30°C.
• This was followed by a colder spell between 21 and 27 September, during which 20 meteorological stations recorded new record-low minimum temperatures for september.
• A heatwave was also recorded between 14 and 20 September, affecting some locations in the inland central region.

Precipitation

• It was the 9th driest September since 2000, with a monthly total of 25.8 mm, corresponding to 60% of the 1991–2020 average.
• Notable rainfall amounts occurred on 27 and 28 September due to the passage of post-tropical storm Gabrielle, which brought significant precipitation to Minho, Douro Litoral, and Beira Litoral regions.

Meteorological Drought

• There was an increase in the area affected by moderate meteorological drought in the southern inland region and in some municipalities of the Tagus Valley.
• By 30 September, 95% of the territory was experiencing mild to moderate meteorological drought conditions.

Click here to have acess to the climate bulletin for september 2025:
https://www.ipma.pt/resources.www/docs/im.publicacoes/edicoes.online/20250918/ZcafqRKykNSKqDFJmsEK/cli_20250801_20250831_pcl_mm_co_pt.pdf

Figure 1. Anomalies of temperature (850hPa), wind (850hPa) and geopotential (500hPa), in September 2025. Source: C3S/ERA5