The 2025 Indian summer monsoon and its 17 western disturbances – beyond unprecedented?

During the 2025 Indian summer monsoon, north India was impacted by 17 western disturbances (WDs) – extratropical storms whose impacts over this region are more typically felt in winter months. WD-monsoon interactions often lead to high impact weather as strong synoptic forcing from the WD meets the monsoon's abundant moisture supply. In 2025, this led to, among others, flash flooding in Mandi (killing 3), the devastating Dharali floods in early August (killing at least 5), and the Kishtwar floods several weeks later (killing at least 50). The total number of WDs, 17, was claimed by the media as record-breaking and unprecedented.

In fact, despite the extraordinary number of high-impact weather events, 2025 was comparable to previous years in terms of WD frequency (2024 had 17 WDs as well; 2023 had 15; 2019 had 22). In this talk, I will identify the large-scale atmospheric conditions present during the 2025 monsoon that led to these WDs being so impactful over north India, and discuss how atypical they were compared to the last 80 years. I will explore the relative roles of climate change and internal variability and ask whether such an unusual season is likely to happen again.