Autumn climatology
As autumn draws to a close, here's a little look back. But first, let's find out how a climatology is arrived at and what it actually tells us.
A climatology describes how normal certain conditions are - in relation to a fixed reference period. It helps us to identify trends, evaluate deviations and classify extreme events in a meaningful way.
The WMO (World Meteorological Organization) recommends 30 years for the reference period: long enough to smooth out extreme years and average out cyclical phenomena such as La Niña and El Niño. It should also be kept up to date to reflect the reality we perceive. Currently, this is 1991-2020, but beware: other reference periods are also used depending on the issues at hand. For example: When talking about the 1.5°C threshold, a pre-industrial period (1850-1900) is generally used.
Modern reanalysis data sets such as ERA5, which combines historical observations with current modeling methods and thus provides global, consistent data back to the 1940s, serve as the data basis.
How normal was autumn 2025?
(All data based on the reference period 1991-2020)
The fall was exceptionally warm globally:
September
September was the third warmest ever recorded worldwide, with +0.66 °C above average. Across Europe, it was even +1.23 °C above average - albeit with regional differences: Portugal, northern Spain, France and the UK were slightly cooler than average, while eastern Europe and Scandinavia recorded the strongest positive anomalies. In terms of precipitation, Spain, the coast of Norway and the Balkans were drier than normal, whereas Iceland, the UK, Fennoscandia and north-western and central Europe received more precipitation than average.
October
October showed an almost identical picture: globally, it was the third warmest October, +0.70 °C above average. In Europe, it was +0.6 °C warmer than normal. However, there have been twelve even warmer Octobers since 1980. In contrast to September, Italy and south-eastern Europe were slightly cooler this time, while the highest anomalies were again in northern Scandinavia - in line with the familiar pattern of particularly strong warming in the polar regions. In terms of precipitation, the Alps, most of the Iberian Peninsula and northern Italy were drier than average. There was more precipitation than normal in eastern Spain, Norway, Sweden and Denmark, parts of southern Spain and, above all, south-eastern Europe.
And November?
November cannot be definitively classified at the moment - the next few days will decide where it ends up in the rankings.
For Austria, the climate monitoring of GeoSphere Austria already provides an initial estimate: According to this, the mountains in particular were slightly warmer than normal and Upper Austria was slightly colder. In terms of precipitation, western Austria in particular was drier than average.
