Methodology — The Weather Extremes Index

Source: KMA surface synoptic (ASOS) daily observations (기상청 지상(종관, ASOS) 일자료) — daily surface observations from the Korea Meteorological Administration (기상청), via the open data portal. Year: 2025, 16 stations. Retrieved 2026-08-29.
Metric definitions — official thresholds, not ours: Heatwave day = daily high ≥ 33°C; tropical night = daily low ≥ 25°C; cold-wave day = daily low ≤ −12°C; rainfall = annual precipitation sum. The thresholds are the KMA’s own advisory criteria — we picked nothing.
Update cadence: Annual — refreshed when a full year of observations closes.

Limits worth knowing before you cite this

One station is not a city. Each city is represented by its main synoptic station; urban heat islands and microclimates within the city are invisible here.
One year is one sample. 2025 rankings are not climate normals — a single typhoon path can move the rainfall order.
Sixteen cities, not all of Korea. We rank major-city stations with long records; the national extremes (highest mountain, wettest island slope) live at stations this index does not cover.