Climatologists from the Korea Institute of Environmental Research, in a study published in Nature Scientific Reports on September 24, 2026, have confirmed that dangerous weather anomalies — extreme heat followed by torrential downpours — are no longer confined to the summer season and have begun spreading into autumn months.
Analyzing 40 years of meteorological data from 57 weather stations (1986–2025), researchers focused on so-called “compound events,” where anomalous heat saturates the atmosphere with moisture, shortly followed by heavy rain. The frequency of such days has surged, with a particularly sharp spike in 2024 and 2025. While the individual events have not become more destructive, the key danger lies in their increasing regularity.
The most alarming finding is a pronounced seasonal shift: these double blows of nature, once tied to the summer monsoon, now regularly occur in autumn. In autumn 2024, the anomaly reached a record 7.29 standard deviations from the historical norm. As global warming allows the atmosphere to hold more moisture, the physical link between heat and subsequent rainfall grows tighter. The authors warn that outdated forecasting models may severely underestimate real climate threats to urban infrastructure and agriculture.
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