How Korea and Japan Are Baking This Summer

About This Chart

Data Visualization Method

• Data: Daily maximum temperature from official weather stations — Korea's KMA (ASOS/AWS) and Japan's JMA (AMeDAS and surface stations). Every value is an observed station daily high.
• Period and area: July 21 – August 3, 2026 (14 days), covering the land areas of South Korea and Japan.
• Selection: Only areas reaching 35°C or higher are shown; cells below that were dropped.
• Processing: Station readings were interpolated onto a 5 km equal-area grid using inverse-distance weighting, run separately for each country so the two were never mixed across the border. A land mask (geoBoundaries KOR/JPN) kept only cells whose center falls on land.
• Chart form: An animated timeline map plays one frame per day. Cell color shows the temperature band, and the timeline can be scrubbed date by date.

Creator's Note

This chart isn't meant to crown whichever country logged the single highest number. The goal was to put Korea and Japan on one comparable surface — same kind of source, same interpolation, same grid — and watch how a single two-week stretch played out. Japan's grids lit up first in late July; southern Korea overlapped as August began.

Korea did edge higher on peak reading this time (42.5°C against Japan's 41.1°C), but the point of the animation is the shared timeline, not the ranking.

Data Sources & Limitations

• Korea Meteorological Administration (KMA), ASOS — Korean station daily maximum temperature.
• Korea Meteorological Administration (KMA), AWS — Korean station daily maximum temperature.
• Japan Meteorological Agency (JMA), AMeDAS — Japanese station daily maximum temperature.
• geoBoundaries (KOR/JPN ADM0) — national land boundaries for the land mask.

The map shows interpolated values, not readings taken everywhere. Only the station sites are real observations; everything between them is estimated. It's official station data resampled onto a 5 km grid, not a "5 km observation network."

Grid counts aren't a measure of heatwave area. At 5 km there are about four times as many cells as at 10 km, and coastal cells count whenever their center sits on land. Because Korea and Japan differ in station density, land area, and climate, cell or station counts can't say whose heat was "worse."

Cell size is only a visual cue that softens the 35°C edge — color carries the temperature, and animation speed is playback timing, not a real rate of change. The grid-interpolated period high (41.63°C) is a separate figure from the station-observed high (42.5°C). ERA5-Land data was not used.