US Environmental Protection Agency
Urban Heat Islands and Climate Change
Overview of heat island causes, impacts and mitigation strategies.
Our work · Urban cooling
Cooling the city, surface by surface.
Applying MEER's passive-cooling research portfolio across the built environment — rooftops, streets, schools, hospitals, markets, transport and informal settlements — as an evolving research and engineering program.
- Applications
- 8
- Technologies
- 5
- Status
- R&D
Cities are heating faster than the planet.
Urban areas are warming faster than surrounding rural landscapes due to the combined effects of climate change and the urban heat island effect. As cities expand, more solar energy is absorbed by buildings, roads and infrastructure, creating hotter environments that threaten public health, infrastructure, water resources and economic productivity.
Cities are becoming increasingly vulnerable to extreme heat.
Concrete, asphalt, brick and dark roofing materials absorb large amounts of solar radiation during the day before slowly releasing that heat through the evening and night. This creates the urban heat island effect, where cities remain significantly warmer than surrounding rural areas, particularly after sunset.
Climate change is intensifying this phenomenon. Rising global temperatures, more frequent heatwaves and expanding urbanization combine to increase heat exposure for hundreds of millions of people worldwide.
Urban heat affects nearly every aspect of city life. It increases electricity demand, places pressure on healthcare systems, accelerates infrastructure degradation, reduces worker productivity, worsens air pollution and disproportionately impacts older adults, children and lower-income communities.
Reducing the solar radiation absorbed by urban surfaces is becoming one of the most effective and scalable strategies for making cities resilient to rising temperatures.
55%+
Over half of the world's population now lives in urban areas — a figure expected to approach 70% by 2050.
up to 12°C
Urban heat islands can leave city centers this much warmer than surrounding rural areas, particularly at night.
~70%
Dark roofs and pavements can account for a large proportion of the solar heat absorbed inside a city.
Millions
Hundreds of millions of urban residents face increasingly dangerous heatwaves as the climate warms.
70°C+
Dark asphalt and rooftop surfaces can exceed these temperatures during summer heatwaves.
Urban heat islands
Buildings and paved surfaces trap heat, keeping cities warmer day and night.
Public health
Extreme urban heat increases heat stress, illness and mortality, especially among vulnerable populations.
Energy demand
Higher temperatures drive air-conditioning use, raising electricity demand and associated emissions.
Infrastructure
Repeated heating accelerates deterioration of roads, buildings, railways and other infrastructure.
How cities heat up
- Sunlight
- Dark surfaces
- Solar absorption
- Heat storage
- Night-time heat release
- Higher air temperatures
- Greater heat stress
Why urban cooling matters
Cooling cities is one of the fastest ways to improve climate resilience.
Unlike many climate interventions that take decades to deliver benefits, reducing urban surface temperatures can immediately lower indoor temperatures, cut energy consumption, improve outdoor comfort and decrease heat exposure.
Reflective materials, cool roofs, passive daytime radiative cooling (PDRC) coatings, reflective canopies, shading systems and other high-albedo technologies all reduce the solar energy absorbed by urban infrastructure.
These approaches complement traditional urban planning measures such as increasing vegetation and expanding tree cover, offering practical solutions that can often be deployed quickly and at relatively low cost.
Cities under rising heat
Select a city to see summer conditions, recent heat records and heat island intensity.
26 cities mapped
Ahmedabad
- Average summer temperatures
- Avg. summer high ~41°C
- Recent heat records
- 2010 heatwave prompted first city heat action plan
- Urban heat island intensity
- UHI up to ~5°C
- Climate vulnerability
- Extreme — outdoor labor exposure
Learn more
Scientific and institutional evidence on urban heat and health.
Read more(opens in a new tab)
World Health Organization
Climate Change, Heat and Health
Fact sheet on health risks from rising heat exposure.
NASA Earth Observatory
Urban Heat Islands
Satellite thermal imagery showing how cities heat relative to their surroundings.
UN-Habitat
Cities and Climate Change
How urbanization and climate risk intersect in cities worldwide.
IPCC
Sixth Assessment Report — Cities, Settlements and Infrastructure
The scientific consensus on urban climate risk and adaptation.
The Lancet
Lancet Countdown on Health and Climate Change
Annual indicators tracking heat exposure and health outcomes.
Keeping cities cooler.
MEER is developing a suite of urban cooling technologies designed to reduce the solar energy absorbed by cities before it becomes heat.
Our work includes reflective roofing systems, passive daytime radiative cooling (PDRC) coatings, high-albedo canopies, reflective pavements and other surface-based solutions that lower urban temperatures while reducing energy demand and improving climate resilience.
Rather than relying solely on energy-intensive air conditioning, these passive technologies aim to prevent heat from building up in the first place — making cities cooler, healthier and more comfortable places to live.
Please note
Research and Product Development
The technologies described on this page are part of MEER's active research portfolio — from reflective roof systems now in field validation, to passive daytime radiative cooling coatings in the laboratory, and modular canopy systems being prototyped in real streets. What differs between urban applications is not the underlying physics but the engineering response to each environment.
We publish progress openly at every stage so other researchers, engineers and communities can build on the work and hold it to account.
[ Passive cooling paint ]
A coating that cools the surfaces a city already has.
Most urban surfaces will never be rebuilt. MEER is developing a passive daytime radiative cooling paint designed to be applied over what is already there — reflecting incoming sunlight and radiating heat out through the atmospheric window, with no power and no moving parts.
The coating is still in laboratory development. Formulations are being optimized for high reflectance, real-world durability and a cost low enough to be usable at city scale.
Learn more about PDRC paint
- Rooftops
Coating existing metal, concrete and asbestos-sheet roofs where full replacement is not affordable.
- Facades & walls
West- and east-facing walls that absorb low-angle sun through the hottest hours of the day.
- Industrial surfaces
Warehouse envelopes, storage tanks and cold-chain buildings with large exposed areas.
- Infrastructure
Transport shelters, water tanks and utility structures across dense urban blocks.
[ Why cities overheat ]
How the built environment stores heat.
Cities become significantly hotter than the countryside around them — a phenomenon known as the urban heat island. The causes are structural: the fabric of the city itself is built to absorb sunlight and release it slowly.
Dark roofs
Absorb more than 80% of incoming solar energy and re-radiate it as heat into rooms below and streets above.
Asphalt roads
Store heat through the day and release it slowly overnight, blocking the city from cooling down.
Concrete & buildings
High thermal mass turns walls and facades into passive heat batteries.
Industrial surfaces
Large impervious plots — car parks, depots, warehouse roofs — amplify local heat loads.
Reduced ventilation
Dense street canyons and reduced airflow trap warm air near the ground.
Lack of vegetation
Fewer plants mean less shade and less evaporative cooling, so surfaces heat more freely.
[ Urban heat island — a diagram ]
The city is hotter because of its surfaces.
A simplified temperature profile from rural land, through suburbs, into the urban core and back out again. Peak temperatures are driven by the density and darkness of the surfaces themselves.
Interactive tool
How hot is your roof?
Explore how colour, material and location shape roof temperatures — and see how much a reflective or radiative surface changes the picture. All numbers use published solar and material physics; MEER technologies use internally validated values.
Peak air temp
34°C
Peak solar
980 W/m²
Low-emissivity metal — retains heat, radiates poorly.
Conventional roof
111°C
Roof surface at solar noon
🔥
Indoor peak
54.3°C
Reflective roof — Reflective coating (MEER)
43°C
Roof surface at solar noon
🌡
Indoor peak
36.3°C
Conventional
Surface
111°C
α = 0.05
absorbs 95% of sunlight
absorbs 95% of sunlight
Reflective
Surface
43°C
α = 0.88
absorbs 12% of sunlight
absorbs 12% of sunlight
Roof surface reduction
-68.0 °C
111°C → 43°C at solar noon
Indoor peak reduction
-18.0 °C
54°C → 36°C peak
Cooling energy saved
60%
~4,320 kWh/yr for 100 m²
CO₂e avoided per year
19,126 kg
Includes 17,182 kg RECO + 1,944 kg from AC
Daily temperature curve
Roof surface across 24 hours
ConventionalReflectiveAir
Time13:00
Air
33.7°C
Conventional roof
108.1°C
Reflective roof
42.6°C
Why the numbers look this way
Data sources: NASA POWER and Global Solar Atlas for insolation; ERA5/Copernicus and NOAA climate normals for air temperature; published engineering values for material solar reflectance and thermal emissivity; MEER internal validation for reflective and PDRC coatings. Estimates are indicative and should not replace an engineering survey for individual buildings.
[ A complementary portfolio ]
Different surfaces need different tools.
No single technology cools every part of a city. MEER's urban research combines multiple approaches so that each surface — a metal roof, a market square, an asphalt junction, an industrial pond — can be met with the most appropriate intervention. The technologies complement rather than compete.
- Reflective Roof Systems
High-albedo treatments that return incoming solar energy skyward instead of storing it in the building fabric.
Typical urban role — Roofs of homes, schools, hospitals, warehouses. - PDRC Coatings
Passive daytime radiative cooling coatings that combine reflection with thermal emission through the atmospheric window.
Typical urban role — High-exposure surfaces, walls, infrastructure. - Canopy Systems
Modular reflective canopies that intercept direct sunlight before it reaches the ground.
Typical urban role — Streets, markets, courtyards, transport hubs. - Floating Reflective Systems
Concept-stage floating covers for water bodies, aimed at reducing solar absorption and evaporation.
Typical urban role — Urban reservoirs, industrial cooling ponds. - Future concepts
Ongoing research into new materials and hybrid systems combining reflectivity, emissivity and durability.
Typical urban role — Applied where existing technologies fall short.
[ Where the portfolio is applied ]
Nine urban environments, one research portfolio.
The same core technologies are engineered differently for each environment. The stage badges show where each application currently sits along MEER's development pathway.
Field Validation
Rooftops
Reflective coatings and PDRC materials applied directly to the largest exposed surface in the city — the roof of every building.
Relevant technologies
Reflective RoofsPDRC Coatings
Field Validation
Schools
Cooler classrooms and shaded playgrounds so children can learn and play through hotter school days.
Relevant technologies
Reflective RoofsCanopies
Prototype Testing
Hospitals & clinics
Protecting patients, staff and equipment from indoor overheating in facilities that cannot afford to fail during heatwaves.
Relevant technologies
Reflective RoofsPDRC Coatings
Prototype Testing
Markets
Modular canopies over open-air markets to protect traders and shoppers from direct sun during peak hours.
Relevant technologies
Canopies
Prototype Testing
Public spaces
Squares, parks and pedestrian routes redesigned so people can safely move through the city on the hottest days.
Relevant technologies
CanopiesReflective surfaces
Concept Research
Transport infrastructure
Research into cooler bus stops, transit interchanges, and reflective surfaces around roads and stations.
Relevant technologies
CanopiesPDRC Coatings
Engineering Design
Industrial buildings
Large low-rise roofs are ideal candidates for reflective and radiative coatings — reducing indoor heat and cooling loads.
Relevant technologies
Reflective RoofsPDRC Coatings
Concept Research
Industrial cooling water
Concept work on reflective floating systems for cooling ponds and process water storage in industrial sites.
Relevant technologies
Floating Systems
Field Validation
Informal settlements
Working with communities where extreme heat is already a daily emergency, applying low-cost reflective systems tailored to local building stock.
Relevant technologies
Reflective RoofsCanopies
[ A neighborhood, not a building ]
Field ValidationFrom individual sites to whole neighbourhoods.
A single cool roof helps one household. A city-wide network of reflective surfaces, PDRC coatings and canopy systems can lower temperatures across whole neighbourhoods — and change how a city feels during a heatwave.
MEER is actively researching how these technologies combine at scale, including modeling, field measurement and long-term monitoring in partnership with local communities.
Reflective roofs across every building
PDRC coatings on high-exposure surfaces
Canopies over streets, markets, squares
Instrumented monitoring at the block level
[ An iterative research program ]
Innovation and deployment research happen in parallel.
Rather than waiting until laboratory work is “finished” before engaging with the real world, MEER develops, tests, measures and refines urban cooling systems through an iterative loop of scientific research and real-world validation.
- Research continues
- Engineering continues
- Materials evolve
- Prototypes improve
- Field validation deepens
- Evidence guides every step
[ Where each technology sits ]
Every application on this page is part of MEER's research and engineering pathway.
We move from concept, through the laboratory, into engineered prototypes and instrumented field trials. Nothing on this page should be read as a finished commercial product unless explicitly described that way elsewhere on the site.
- Stage 01
Concept Research
- Stage 02
Laboratory Development
- Stage 03
Engineering Design
- Stage 04
Prototype Testing
- Stage 05
Field Validation
- Stage 06
Future Deployment
[ Related ]
Continue exploring the research program
Our Technologies
The full research and engineering portfolio behind every urban application.
ExploreUnderstanding Albedo
Why reflectivity is the physical lever behind every urban cooling strategy.
ExploreRadiative Cooling
How selective emitters send heat past the atmosphere to cold space.
ExploreCooling Return on Investment
How urban interventions compare on cooling delivered per unit of energy input.
ExploreHeatLens
Our beta risk platform combining temperature, humidity and radiant heat.
ExploreNews & Stories
Field updates from partner cities and communities.
Explore[ Join the research ]
A research program for the world's hottest cities.
If you are a city, researcher, engineer or partner working on urban heat, MEER would like to hear from you. The portfolio evolves faster when it is shaped by the places it will serve.