Malaysia’s capital has experienced rapid growth as a population and business centre in the past three decades. New townships, skyscrapers, industrial centres, and highway networks are part of the urban sprawl that has come to overwhelm and replace the once-green landscape of Greater KL. This rapid growth comes at a hidden cost—our urban areas are both generating heat while losing the ability to mitigate temperature increases. Climate change is an additional factor.
To illustrate the scale of this warming, The Habitat Foundation funded a Heat Map Study of Greater KL by scientists from Think City.
Using historic satellite data from NASA’s Landsat programme, the study assessed Land surface temperatures (LST) across the Greater Kuala Lumpur region between 1990 and 2023. The study analysed patterns in the temperature of the ground, roads, rooftops, and vegetation.
The findings are striking. Within the study area, across parts of six districts spanning the Klang Valley, from urban centres in Kuala Lumpur and Petaling Jaya to the forested hills of Gombak and Hulu Langat, the maximum land surface temperatures has risen by as much as 2.9°C. A noticeable factor contributing to this change has been a loss of urban green spaces and forest cover.
Greater KL’s trajectory is worth taking seriously. This study maps how warming is unfolding and why addressing it now matters before the heat becomes a permanent feature of city life.
Tracking Heat Across the Landscape
To understand how urban heat has changed over time, the study focused on three key indicators:
- The first is the spread of high-heat zones, specifically areas where land surface temperatures exceed 30°C. This threshold is widely associated with urban heat island conditions, where dense built environments trap and radiate heat far more than natural landscapes do.
- The second is the shrinking of cool zones, areas where land surface temperatures stay below 25°C. These cooler patches are typically shaded by trees, near rivers or water bodies, or simply less developed. They act as natural relief valves for the city, keeping local temperatures down and making surrounding areas more liveable.
- The third is what is happening at the extreme end, the hottest 10% of the study area. Tracking this group over time reveals whether the most intense heat is becoming more widespread and more severe.
Together, these three lenses tell a fuller story: heat is not just rising gradually across the board. It is expanding into new areas, pushing out the cool zones that once provided relief, and intensifying at the extremes in ways that average figures alone would never capture.
Cities Getting Hotter
The scale of change becomes stark when the numbers are placed side by side.
In 1990, just 0.56% of the study area recorded land surface temperatures above 30°C. These high-heat zones were modest in size, clustered around early development areas near Subang, Kepong, and Ampang, and tracing the edges of major highways. By 2023, that figure had increased to 13.6%, with hotspots spreading well beyond central Kuala Lumpur into Gombak, Hulu Langat, Puchong, Subang Jaya, and Klang.
The loss on the other side of the ledger is equally significant. In 1990, roughly 33.9% of the study area remained naturally cool, with land surface temperatures below 25°C, mostly across forested and agricultural land in Gombak, Hulu Langat, and Kuala Selangor. By 2023, that share had fallen to 25.9%. What were once broad stretches of cooling landscape are now increasingly confined to isolated forest reserves, hill slopes, and the shrinking patches of agricultural land that remain.
More built-up land. Less natural cover. The two trends are part of the same story.
Heat Intensification
The data also shows that the heat is not just spreading, it is intensifying.
In 1990, the hottest 10% of the study area peaked at 33.0°C, concentrated largely in central Kuala Lumpur and its immediate surroundings. By 2023, that ceiling had climbed to 36.0°C, a three-degree jump in just over three decades. At the same time, these extreme heat zones have expanded to cover a much wider stretch of the Klang Valley.
In other words, the extremes are getting more extreme. The hottest spots are hotter than they have ever been, and there are more of them.
Urban Growth and Rising Heat
Petaling Jaya offers one of the clearest examples of how rapid development and rising temperatures move together.
In the 1990s, areas like Setia Alam, Kota Damansara, Subang Bestari, and Bandar Saujana Utama were largely low-density or green. Today, they are dense residential neighbourhoods, industrial zones, and commercial districts. The transformation has been dramatic, and the temperature data reflects it.
As concrete, asphalt, and rooftops replaced trees and open land, surface heat followed. The more built-up these areas became, the hotter their land surfaces grew, making Petaling Jaya a telling case study in how the choices a city makes about land use shape the temperature its residents ultimately have to live with.
Why This Matters
Heat does not have to be an inevitable consequence of growth. But addressing it requires policymakers, urban planners, and city leaders to first see it clearly, and that is precisely why studying urban heat trends is important. By mapping how heat patterns have shifted over more than three decades, the study translates a complex, slow-moving problem into something visible, comparable, and hard to ignore.
The findings also serve as a reminder of what is still worth protecting. Forests, green corridors, and natural hills remain the city’s most reliable cooling infrastructure, quietly regulating temperatures across the wider metropolitan area. Where they persist, they offer relief. Where they have been lost, the heat data shows the consequences.
The purpose of this study has been to stimulate an urgent conversation among decision makers and developers that have the opportunity to influence the capacity for Greater KL to weather the challenges of climate change. Current planning frameworks acknowledge climate change, but do not yet sufficiently prioritise the protection of green-built ratios or explicitly integrate heat metrics into land use and development control decisions. Without stronger safeguards, continued urban sprawl risks locking in higher heat exposure, increased health burdens, and declining urban liveability.
Heat affects all of us, but the ability to cope differs according to our exposure and vulnerability. Children, elderly, and outdoor workers are more exposed to or impacted by heat stress. The ability to access air-conditioning is not available to us all equally. At the same time, increased aircon use contributes to higher energy consumption, higher bills, and further increases to urban heating. Economic impacts should also be considered more comprehensively – such as impacts on productivity, public health, and even declines in tourism arising from uncomfortable temperatures.
Evidently, this is an important multi-sectoral issue; more agencies and experts should be enlisted in a common conversation to tackle the challenges and assess mitigating measures. This should include safeguarding green areas which are a nature-based solution we should be careful to safeguard.
This pilot study highlights the need for follow-on research: integrating ground-based temperature monitoring, linking LST changes to zoning and development approvals, and testing cooling interventions at neighbourhood scale. Strengthening these evidence pathways can support DBKL and Selangor local councils to embed heat resilience into planning guidelines, infrastructure investment, and future urban growth strategies.
Read the full report here.
Featured in The Edge Malaysia
Our Greater KL Heat Map Study was also featured in The Edge Malaysia.
Read the coverage → https://theedgemalaysia.com/node/792811
Watch a panel discussion on The Shift Asia with Freda Liu → https://www.facebook.com/share/v/1CN5RhrXLp/
