Seoul is operating fine-mist cooling systems at 235 locations and cooling-road sprinklers across 5.67 kilometers, while 199 street-washing trucks cover 2,163 kilometers of road up to eight times a day during heat advisories.

The heat came early this year. South Korea recorded a heat-related death on May 15, before summer had properly started — the earliest such death since the country set up its emergency-room heat tracking in 2011. By early August, Seoul had issued its first-ever citywide highest-level heat warning.

A city facing that kind of season has a choice: treat each hot spell as a crisis to survive, or build the response into the streets themselves. Seoul has spent the last few years choosing the second option, and the 2026 numbers show how far that thinking has gone.

Below we look at the water-based and reflective measures the city is running this summer, and what a plan this size says about how cities are starting to handle hot weather.

Most of it comes down to one problem: the urban heat island effect. Asphalt and concrete soak up sun and hold onto it, leaving dense cities several degrees hotter than the countryside around them. Almost everything here is an attempt to push back against that.

Fine-mist fog systems at 235 sites

The most visible piece is the cooling fog.

As of August 2, 2026, Seoul had 187 cooling-fog installations in operation, with plans to add another 48 and expand the network to 235 locations this year.

They spray fine droplets of water into the air over plazas, parks and crossings. As the mist evaporates, it pulls heat out of the surrounding air — the same reason stepping out of a pool on a breezy day feels cold.

Cooling roads across 5.67 kilometers of pavement

A stranger measure, and one of the more interesting, is the cooling road. Sprinklers along the roadside wet the asphalt directly, so the pavement cools as the water evaporates. As of August, Seoul had extended this grid to 5.67 kilometers across 19 locations, mostly near transit hubs such as City Hall Station where crowds gather at street level.

According to the city, the effect is measurable. Park Wan-song, who heads Seoul’s Road Management Division, said: “Operating the cooling roads typically lowers asphalt roads’ surface temperatures by 7 to 11 degrees Celsius.”

During the August heat wave, thermal imaging showed treated roads sitting around 36 to 37 degrees Celsius, while nearby untreated roads read close to 50. Each run uses two to seven tons of water. Under the highest warning, the sprinklers ran as often as nine times a day at hourly intervals.

199 street-washing trucks over 2,163 kilometers

The biggest measure by sheer coverage is the truck fleet. During heat advisories, 199 water-spraying trucks cover 2,163 kilometers of road, with fixed-site washing running up to eight times a day. The trucks spray water across major and local roads, wetting far more ground than the fixed cooling-road grid can reach.

On August 4, when more than 200 trucks covered about 7,000 kilometers across Seoul in a single day. A city official described it as “the largest water-spraying operation in the city’s history.” 

Cool-roof coatings on 204 buildings

Not everything on the list involves water. Seoul is also applying reflective coatings to the roofs of 204 buildings, starting with aging housing and welfare facilities where residents feel indoor heat the most. A cool roof reflects sunlight instead of absorbing it, so less heat soaks into the building below.

This is the permanent end of the plan. No fleet to send out, no daily operation to run. Once the coating is on, it keeps reflecting sun through every hot day for years. The people it protects most are often the ones least able to run an air conditioner, which is part of why the city started there. The World Resources Institute makes the same basic point about the physics, noting that dark, sealed surfaces trap heat while lighter and moister ones shed it.

Roughly 4,078 public cooling centers

Behind all the engineering sits the simplest measure of all: somewhere cool to go. Seoul runs roughly 4,078 public cooling centers across the city, air-conditioned rooms in community halls, welfare buildings and other public spaces where anyone can sit out the worst of the afternoon.

The fog canopies and cooling roads make the outdoors more bearable in passing. The cooling centers are for people who can’t just pass through, older residents especially, for whom a few hours of shade and cold air is the difference that matters. 

What a heat plan at this scale tells us

Perhaps the most telling thing about the 2026 plan is how routine it all sounds. Fixed sprinkler grids, a set truck rotation, a coating program, a standing network of cooling rooms. This is the language of infrastructure and maintenance, not emergency response. A city that treats heat as a regular feature of its climate builds standing systems for it, the way it already does for rain or snow.

The evidence supports the general shape of this approach, even if no single city’s numbers transfer cleanly to another. Reviews of urban cooling work find that reflective surfaces and evaporative cooling can each take a meaningful amount off local surface temperatures. The World Resources Institute notes that Phoenix cut surface temperatures in some areas by over 7 degrees Celsius through reflective techniques. Water and reflection genuinely help. What they don’t do is fix the root problem, which is why researchers tend to pair these measures with longer-term shade and greening.

As far as we can tell, the real signal here is not any single figure but the mindset behind the whole list. Seoul isn’t reacting to a bad summer. It’s assuming bad summers, and building the response into the city’s daily operation so it’s already running when the temperature climbs. For other cities watching their own thermometers creep up, that shift from scrambling to planning may be the most useful thing to copy.