A summer in which the air shimmers and the nights bring no relief from the heat. Many people now know this from personal experience. Yet even the extreme summers of past decades may not yet reveal the kind of heat that is possible in today’s climate. The next extreme summer could surpass anything we’ve experienced so far. This is shown by a new study from the University of Leipzig.
The research team investigated what a so-called “century summer” might look like in today’s climate. This refers to an exceptionally hot summer that, statistically, occurs about once every 100 years. The study reveals that late summer, in particular, is warming significantly. In the part of Western Europe studied, the last week of July has warmed by 1.4 degrees more than the first week of June. At the same time, soils tend to be drier today.
“As a result, there is now a longer period in late summer during which favorable weather conditions, combined with very dry soil, can lead to extreme and prolonged heat,” explains Dr. Peter Pfleiderer, lead author of the study at the Institute of Meteorology at the University of Leipzig. This refers, for example, to prolonged high-pressure systems with little rain.
Many extreme summers simulated on a computer
To investigate such rare events, the researchers simulated many possible summers on a computer. They terminated calculations early if they did not develop toward extreme heat. This allowed them to compare “once-in-a-century summers” under current and pre-industrial climate conditions. The study defines these based on the average temperature over the entire summer.
However, the study is based on a single climate model. Further models are therefore needed to determine how robust the results are. In addition, the Leipzig researchers intend to investigate the influence of large-scale weather patterns on extreme summers and how “once-in-a-century summers” develop in other parts of Europe.
Original publication:
Pfleiderer, P., Noyelle, R., & Sippel, S. (2026). Heat extremes within hot summer seasons intensify more than in average summers under global warming. Earth's Future, 14, e2026EF008241.
