Urban Heat Pollution in the Capital Region

The urban heat island (UHI) effect is the warming of urbanized areas relative to their surrounding, vegetated, rural regions. Traditional building and infrastructure materials — like concrete and asphalt pavements — retain more heat during the day and release it back into the environment, increasing surrounding temperatures. Coupled with summer heat, urban heat has implications for all of us, because excessive heat:

  • Negatively impacts health and well-being by exacerbating chronic and acute conditions (which increase emergency room visits and death rates, particularly for the most vulnerable populations);
  • Increases electricity use — which can increase the costs for cooling, stress power generation and transmission systems, and increase greenhouse gas emissions;
  • Negatively impacts our economy by reducing agricultural and labor productivity, among other factors;
  • Impairs water quality and increases the volume of water required to keep trees and landscape alive and healthy.
Heat & the Capital Region

What is Regional Heat Pollution?

Although the traditional term “urban heat island” implies that the effects are isolated to urban city centers, the Capital Region is unique. Due to the Delta Breeze — a movement of cooler, ocean air via the Delta into hotter valley air — heat is not confined to the urban areas. The excess heat produced from the built environment and the use of internal combustion engines migrates to the surrounding areas in the northern and eastern parts of the region, including:

  • Citrus Heights
  • Arden-Arcade
  • Carmichael
  • North Highlands
  • Rio Linda
  • Fair Oaks
  • El Dorado Hills
  • Roseville
  • Folsom
  • Rocklin

The urban heat island effect is therefore a regional heat pollution problem. In other words, addressing the impacts of heat in the region requires a multi-agency and multi-jurisdictional collaborative effort.

In 2012, the California Legislature tasked the California Environmental Protection Agency to develop an Urban Heat Island Index that would quantify the extent and severity of the urban heat island for cities. The resulting (above) maps reflect the increase in temperatures caused by the urban heat island and not the total heat. Among other things, the study found that the index tends to increase during heat waves. The study also found that wind and topography can move the generated urban heat to surrounding areas. Looking at the map for the Sacramento region, the generated heat moves to areas including North Highlands, Roseville, Auburn, and El Dorado Hills.

We are currently working to expand awareness of the urgent need to address heat pollution in multiple sectors to protect the health and vitality of our region, both now and in the future. One key initiative is a project focused on identifying the most effective urban cooling strategies for the region, creating a map of polluting sources contributing to the urban heat, and developing a plan to reduce regional heat pollution.
Heat & Implications

Although we might dismiss summer heat as normal, summer temperatures are rising and expanding into both the spring and fall seasons.

It’s Not Your Imagination. Summers Are Getting Hotter.
Extraordinarily hot summers – the kind that were virtually unheard-of in the 1950s – have become commonplace. This year’s scorching summer events, like heat waves rolling through southern Europe and temperatures nearing 130 degrees Fahrenheit in Pakistan, are part of this broader trend. Read the entire article on nytimes.com>

Spring has arrived early for much of the US. It’s gorgeous — and concerning.
On February 21, it reached 80 degrees in Washington, DC — the earliest date on record to achieve a temperature so high in the city. Since then, the weather has been unusually mild, and the environment has responded accordingly. Read the entire article on vox.com>

What if the heat does not affect me?

Say hello to optimism bias.

Optimism bias is the difference between a person’s expectation and the resulting outcome. As humans, we have a natural tendency to overestimate the likelihood of positive events, and underestimate the likelihood of negative events. In short, optimism bias can lead us to think that we can escape any negative risks. In this case, heat. 

The truth is, heat affects all of us. It impacts our:
  • Public Health.
  • Energy Demand.
  • Economy.
  • Agriculture.

Public Health

From Discomfort to Death

Energy Demand

More Cost and (for now) Pollution


Yes, Heat Pollution Costs Us Money


From Our Food Supply to Livestock
Heat & Health

Heat and the Vulnerable

Heat affects us all. However, some of us are at greater risk. Heat disproportionately affects individuals based on their age, health, and living conditions such as living in substandard housing, experiencing homelessness, and living in social isolation. Most of us have at least one friend or family member who falls into one of the following categories:
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    Older Adults

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    Infants & Children

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    Outdoor Athletes

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    Outdoor Workers

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    People with Pre-Existing Medical Conditions

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In the Short-Run, We Beat the Heat

Heat-related deaths and illnesses are preventable. The following are some individual efforts you can take to reduce immediate heat risks.
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    Be Informed

    Check the local weather report and your city/county website for alerts.

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    Stay Hydrated

    Drink plenty of water. Consult with your doctor if you are on medication or have a medical condition regarding water/fluid intake. 

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    Limit Alcohol & Coffee Intake

    Alcohol and caffeine increase your risk of dehydration.

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    Limit Hot Food Consumption

    Eating hot foods limits your body’s ability to cool itself.

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    Stay Cool

    Seek refuge inside a cooling center (an air-conditioned public space such as a library, a movie theater, etc.). Check your city/county website for cooling center locations.

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    Weather-Appropriate Clothing

    Consider wearing lightweight, light-colored, loose-fitting clothing, and a hat.

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    Check on family and community members. Talk to family and community members about their own potential risks.

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    Limit Unnecessary Outdoor Exposure

    Limit outdoor exposure during peak daytime temperatures. When possible, plan outdoor activities in the morning and/or in the evening, and remember to use sunscreen/sunblock.

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    Keep an eye on kids/pets

    Do not leave kids or pets alone in a vehicle (inside temperatures increase dramatically).

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    Fan Use

    Do NOT use electric fans when the temperatures outside reach more than 95°F. Fans create air flow and a false sense of comfort, but do not reduce body temperature. You could increase your risk of heat-related illness. 

Heat & the Built Environment

How Hot is Hot?

There are many contributors of heat, and one of them is the urban infrastructure. The loss of natural vegetation results in a decrease in shade and evapotranspiration (the water transfer from the land to the atmosphere) — which are both natural cooling mechanisms. Furthermore, traditional urban surfaces (cement and asphalt) absorb more heat during the day, even more so if they are not shaded, and once these surfaces reach thermal equilibrium (similar temperature) with their surroundings, they release the absorbed heat (typically during the evening hours) into the surroundings, warming the surrounding air.

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To address heat and the built environment, we can start by looking at the following:
  • Cool Pavements.
  • Cool Roofs.
  • Trees.
  • Green Roofs.
  • Cool Walls.


Cool Roofs

Cool Pavements

Cool Walls

Green Roofs

Why Trees and Cool Roofs? Proven Solutions

Research suggest that urban planning that incorporates more trees, cool roofs, and alternative materials for urban infrastructure can help mitigate the urban heat island effect. Though all five mitigation strategies help reduce heat and ozone pollution, protect health, and save energy, cool roofs and trees are, for now, more economically feasible and heavily supported by research.

Utility Rebates

If you are a SMUD customer, take a look at their Shade Tree and Cool Roof Rebate programs.  If you are a Roseville Electric customer follow the link to their Shade Tree rebate program. And if you are a PG&E customer, visit their Rebates page.
Regional Efforts

1. Shading the Region

2. Home Energy Programs

Home retrofits can save you electricity and money. The following organizations offer programs to increase your home’s energy efficiency:

3. SB-1 Adaptation Planning Grant to Reduce the Urban Heat Island Effect

The Sacramento Metropolitan Air Quality Management District (SMAQMD), in collaboration with the Local Government Commission and other Capital Region Climate Readiness Collaborative (CRC) members, will develop an in-depth exploration of how the UHI effect will impact the Capital region, and develop a blueprint of solutions. The extent to which urban areas can effectively combat the UHI effect depends on various factors, including meteorology and climate, geography, emissions, land-use patterns, proximity to bodies of water, and albedo. Given the region’s unique UHI pattern and climate, the project — which is funded by the California Department of Transportation’s SB1 Adaptation Planning Grant — will allow us to explore which solutions are more effective for the Capital region.

Project Goal |
Provide a blueprint that will transform the transportation sector from a heat source to a cooling solution so as to prolong infrastructure lifespan, support active transportation, reduce GHG emissions, and improve air quality.
Project Concept |
Source: CalEPA
Heat Island Model

The 2015 CalEPA study is the catalyst for this project. The study revealed that because of the region’s wind patterns and topography, the UHI effect is not confined to the urbanized areas, but rather spreads to the surrounding suburban and foothill areas.  

Cooling Solutions

Analyze the effectiveness of potential mitigation measures — trees, cool roofs/walls/pavements, electric vehicles, green roofs.  

Transportation Plans

The transportation sector, including its miles of roads and highways, as well as vehicle emissions is a key contributor to the urban heat island effect. The infrastructure is also vulnerable to extreme heat events — prolonged exposure to extreme heat can damage roads and highways, increasing the cost of maintenance.

Community Input

Input from vulnerable communities on their transportation needs, concerns, and priorities will be incorporated into the strategies and recommendations aspect of the project.

Project Deliverables |
  • A publicly available, regional UHI model that identifies the areas most affected by extreme heat and analyzes the effectiveness of mitigation measures —cool roofs, tress/vegetation, electric vehicles.
  • Recommendations for heat resilience incorporated into current and future transportation plans, codes, projects, and design guidelines
  • A heat reduction plan that incorporates community input on neighborhood and transportation priorities, transportation plans, cooling strategies, and the developed urban heat island model. 

Contact Shelley Jiang at sjiang@airquality.org or Julia Kim at jkim@lgc.org if you would like to learn more about this project or would like to become a partner on this project. 

Heat Outside the Capital Region

From Sacramento to Europe

Everyone is affected.
More than 90 deaths now linked to heat wave in Quebec
More than 90 people are now suspected to have died as a result of a July heat wave in Quebec, with new figures that 53 deaths in the city of Montreal alone may be linked to the elevated temperatures. Read the full article on thestar.com>
Heat is Easing in Europe, but Not for Leaders in France.
While Europe’s record heat wave has begun to moderate, the recriminations for what is only now being recognized as an epidemic of heat-related death are just beginning. Read the full article on nytimes.com>
Here’s how heat discriminates, and what Phoenix is doing to help those at risk
As temperatures rise from the forces of climate change and a widening urban heat island, vulnerable populations will suffer disproportionately. Read the full article on azcentral.com> 
Emergency personnel respond to record number of calls as heat wave kills 10 more in Japan
Exhaustion and heat stroke caused by scorching summer temperatures on Thursday killed 10 people in seven prefectures and sent 2,605 people to hospitals, according to the latest figures.  Read the full article on japantimes.com.jp> 
As temperatures rise, so do the hidden dangers of urban heat
If heat is the enemy, Marcela Herrera thought she was ready for battle last summer at her family’s north Los Angeles apartment. Old air conditioner units chugged away on windows in three rooms. Extension cords snaked into box fans on the floor, positioned along a hallway to push cooler air towards warmer spots. Continue reading on curious.kcrw.com>
California’s 2006 heat wave was much deadlier than previously reported, researchers say.
New analysis of data in nine counties, including L.A., San Bernardino an Kern, indicates that 350 to 450 heat related deaths may have occurred — two to three times more than coroners’ counts. Continue reading on the latimes.com>
From 122 degrees in Death Valley to 100 in Sacramento, heat wave to plague California this week.
Sweltering heat will plague much of California this week and increase snowmelt along the Sierra Nevada, forecasters said. Starting Thursday, a heat wave will grip the mountains, deserts, valleys and major cities for several days as temperatures soar into the 90s and 100s. Read the full article on latimes.com>
An Oral History: Heat Wave.
In July 1995, a scorching three-day stretch caught the city unprepared, leaving 739 dead. The key players recount how one of Chicago’s worst disasters unfolded. Read the full story on chicagomag.com>
As heatwave kills more than 600 across India, Ahmedabad action plan shows how lives could be saved.
A searing heatwave has hit large parts of India with parts of Telangana and Uttar Pradesh seeing temperatures as high as 48°C. More than 600 people have been killed by the heat this summer, as per news reports. Continue reading on scroll.in>
Want to Survive Climate Change? You’ll Need a Good Community
In the summer of 1995, a blistering heat wave wave settled over Chicago for three days. It killed 739 people, making it one of the most unexpectedly lethal dissater in modern American history. Continue reading on wired.com>

Be Informed, Stay Informed.

The information presented on this site is only the beginning. We encourage you to continue your own research and understanding. You can get started by clicking any of the links below to learn more about the impacts of heat.

In 2017, the National Weather Forecast released HeatRisk — a forecast providing a quick view of heat risk potential for the upcoming seven days.  For each of the 5 levels, the tool explains the meaning, who/what is at risk, the commonality of the heat, and covers what actions can be taken.

Find more resources for preventing and treating heat-related illness on the California Department of Public Health website.

Cal-Adapt allows you explore how climate impacts will affect California. Explore the tool to see how heat will impact the region.

Want a more scientific understanding of the impacts of heat? Read the Temperature-Related Death and Illness chapter of the Climate and Health Assessment.

Can’t get enough trees? Read the full Planting Healthy Air report.

Interested in learning about all of heat’s potential implications for  the human body? Researchers at the University of Hawai’i have synthesized 27 physiological pathways in which exposure to heat can result in death, from ischemia and heat cytotoxicity to renal failure.

The Increasing Dangers of Heat

The dynamics and implications of heat are changing.

Heat makes you dumb, in four charts
Man, it’s a hot one. And that could mean bad news for your performance at work or school, according to at least four recently published studies. Read the full article on washingtonpost.com>
Nights Are Warming Faster Than Days. Here’s Why That’s Dangerous.
July kicked off with searingly hot temperatures for most Americans this year. New daily, monthly and all-time record highs were set across the country last week, with more than 100 million people sweating it out under heat warnings or advisories. Read the full article on nytimes.com>
Summer Nights Are Getting Hotter. Here’s Why That’s a Health and Wildfire Risk.
Higher nighttime temperatures as the climate changes can leave homes and humans little chance to cool off. It’s affecting agriculture and wildfire activity, too. well after dinner time in Southern California on Friday, the thermometers read 100 degrees. Read the full article on insideclimatenews.org>