Seoul crosses 40°C for the first time in eight years
Seoul recorded 40.2°C for the first time since 2018, with nearby Hanam hitting 40.7°C as the heat wave peaked
The three lines
- Seoul's Nowon district hit 40.2°C Friday — the capital's first 40-degree reading since August 2018
- Hanam reached 40.7°C, the national high; tropical-night days are at a record 13 for the period
- Power demand may top the all-time peak of 97.1GW; Typhoon Dolphin's path is the wildcard
Key questions
- How unusual is 40 degrees in Seoul
- Genuinely rare. Friday's 40.2°C at the Nowon observation point was Seoul's first reading above 40 since August 1, 2018. Neighboring Hanam logged 40.7°C, the national high, and Gwangyang in the south also entered the 40s. It came on Ipchu — the traditional calendar day marking autumn's start.
- Is this heat wave record-breaking overall
- On the night side, yes. From June 1 to August 6, Korea averaged 14.8 heat-wave days (fourth most since records began in 1973) and 13.0 tropical nights — nights above 25°C — the most ever for the period. Days near records and nights at records means the country never cools down.
- Is the power grid at risk
- It is under watch. Cooling demand may push past the all-time peak of 97.1GW set in August 2024. When demand approaches supply capacity, the reserve margin thins and staged emergency measures kick in — the mechanics are in today's reference, 'Korea's power reserve margin explained.'
The traditional calendar declared autumn; the thermometers declared otherwise. On Friday — Ipchu, the day Korea's lunisolar calendar marks the start of fall — Seoul's Nowon observation point hit 40.2°C, the capital's first 40-degree reading since August 1, 2018. Hanam, just east of Seoul, reached 40.7°C, the highest in the country. This page does not routinely cover weather; today the number is the biggest domestic story there is.
1. Record days, record nights — heat that never switches off
What distinguishes this heat wave is that day and night are breaking records together. From June 1 to August 6, the national average count of heat-wave days reached 14.8 — fourth most since records began in 1973. Tropical nights — nights that never drop below 25°C — hit 13.0, the most ever for the period. When nights stay hot, buildings and asphalt never shed their heat, and each day's climb starts from a higher floor.
Behind the heat sits a typhoon. Typhoon Dolphin, the season's 13th, is tracking past Okinawa into the East China Sea. If it pushes toward China, it props up the Pacific high that forms Korea's heat dome — intensifying the very heat wave it bypasses. A direct landfall on the peninsula is currently rated unlikely; the storm's final path will decide next week's temperatures.
2. The records at a glance
| Item | Figure | Note |
|---|---|---|
| Seoul Nowon (Aug 7) | 40.2°C | First 40+ in Seoul since 2018 |
| Hanam, Gyeonggi | 40.7°C | National high (40.8 in some reports) |
| Gwangyang | 40s | Southern coast |
| Heat-wave days (Jun 1-Aug 6) | 14.8 avg | 4th most since 1973 |
| Tropical nights | 13.0 | Record for the period |
| Power demand | May top 97.1GW | All-time peak, Aug 2024 |
| Weekend outlook | Easing | Highs 26-35°C |
The immediate operational worry is electricity. Cooling demand may push past the 97.1GW all-time peak, and as demand closes in on supply capacity, the reserve margin thins toward staged emergency measures — for global readers, Korea runs one of the world's most air-conditioner-dense grids, and summer peaks are a national event.
3. What remains
The weekend brings relief — highs of 26-35°C — but Dolphin's path could rebuild the heat dome next week. Two numbers await confirmation: whether the power peak record actually fell, and Hanam's official maximum. How Korea's staged power emergency works is in today's companion reference, "Korea's power reserve margin explained"; the heat-warning system itself is in the standing reference "Heat wave alerts."