Extreme Heat and Urban Heat Islands

Learn where the heat islands are in Fairfax County, how you can protect yourself and your family, and what Fairfax County is doing to adapt to extreme heat and help reduce heat islands.

Many places, including Fairfax County, are seeing hotter weather and more extreme heat than in previous years. 

When heat strikes, neighborhoods with less greenery and more buildings and pavement can get much hotter than surrounding areas. These hot spots, known as Urban Heat Islands, can have warmer temperatures during the day and at night, making it difficult for people to keep cool in these areas. 
 

Heat Islands in Fairfax County

Annandale, Bailey’s Crossroads, Centreville, Hybla Valley, Merrifield, Seven Corners, Springfield, and Tyson’s Corner are some of the hottest areas in Fairfax County. 

View the county’s Resilient Fairfax interactive map to see average temperatures in your neighborhood and across our communities. Explore different features showing population data, transportation options, and natural resources like tree canopy, parks, and bodies of water.


 

Who is at Risk?

Everyone can be affected by heat, but some people are more at risk than others, especially if they work, live, or exercise in heat islands:

  • People who work outside, such as construction workers, landscapers, emergency responders, arborists, trash/recycling crews, delivery drivers, and park employees, because they spend a lot of time outdoors and often perform strenuous activity while outside.
  • People who live in urban heat islands, particularly if they don’t have reliable access to air conditioning or transportation.
  • People who exercise outside, including children, students, and adults, are more likely to become dehydrated and get heat-related illness.
  • Economically disadvantaged communities, because they are more likely to lack access to air conditioning.
  • Older adults, children, and people who are pregnant, because they are more sensitive to heat and their bodies have a harder time cooling down.
  • People with chronic medical conditions, disabilities, or access and functional needs, because heat can worsen existing symptoms, increase strain on the body, and interfere with certain medications. 
  • People experiencing homelessness, who typically have less access to cooling and transportation. 

How Extreme Heat Can Affect Your Health

Heat-Related Illness: High heat can cause heat-related illnesses such as heat stroke, heat exhaustion, and dehydration. So far this summer (5/1/25-7/24/25), there have been 184 heat-related illness visits to emergency departments or urgent care centers in the Fairfax Health District, compared to last summer’s total count of 216 visits (from 5/1/24 – 9/1/24).

Know the signs of heat-related illness and what to do:

  • Heat Stroke – Heat stroke is a medical emergency – call 911 immediately! Symptoms include extremely high body temperature (above 103°F), red or dry skin, rapid pulse, dizziness, confusion, seizures, or unconsciousness. Move the person to a cooler place if you can and use cool cloths or a cold bath to lower body temperature.
  • Heat Exhaustion – Symptoms include heavy sweating, weakness, dizziness, tiredness, cool or clammy skin, headache, nausea or vomiting. Move to a cooler spot (preferably air conditioned); take a cool bath or apply cool, wet cloths to your body; and sip water. Seek medical help if symptoms worsen, last more than an hour, or include vomiting.
  • Dehydration – Occurs when the body loses more fluids than it takes in. Symptoms include dry mouth, fatigue, dizziness, dark-colored urine, or muscle cramps. Sip water or electrolyte drinks to rehydrate. Limit caffeine and alcohol consumption. 

Exacerbation of Chronic Conditions: Heat can worsen health conditions such as heart disease, respiratory illness, and kidney disease, and can make it harder for the body to keep itself cool. 

Interrupted Community Lifelines: In areas that frequently experience high heat, critical systems like electricity, transportation, and hospitals can be disrupted. 

  • As more people run air conditioners, strain on the power grid can lead to electricity outages. 
  • Roads and train tracks can be damaged by extreme heat.
  • Hospitals, businesses, and other facilities may have to close or limit operations due to power outages.

For more information on heat vulnerabilities, please see the Resilient Fairfax Vulnerability and Risk Assessment. 
 

Protect Yourself and Your Loved Ones

Staying out of extreme heat is the best defense against heat-related illness. If you live or work in an urban heat island or spend time outside during extreme heat, take steps to stay cool, stay hydrated, and limit your exposure:

  • Frequently monitor the local heat index (temperature and humidity) using a trusted weather source.
  • Never leave people or animals in parked cars if the engine and air conditioner are off. 
  • Understand your personal risk. Children, older adults, outdoor workers, and people with chronic medical conditions are some of the groups at increased risk.
  • Drink water regularly. Don’t wait until you’re thirsty!
  • Stay inside during the hottest part of the day (usually 10 a.m. to 4 p.m.).
  • Wear loose, light-colored clothing, a wide-brimmed hat, and sunscreen with an SPF of 30+ when outside.
  • Identify nearby air-conditioned places you can go to stay cool, such as a shopping mall, library, or Fairfax County cooling center.
  • Talk to a healthcare provider about how heat may affect your health conditions and medications.
  • Don’t rely solely on a fan. Fans move air but do not cool the air or lower body temperature.
  • If you need help with air conditioning at home, apply to one of the county’s cooling programs (Cooling Assistance, Senior Cool Care, or AC Rescue)

Employers of Outdoor Workers

If you employ people who work outside in urban heat islands or other hot areas, consider taking the following steps to protect your workers:

  • Provide access to cool, fresh drinking water and encourage workers to drink frequently, even if not thirsty. 
  • Reduce outdoor work time and decrease work intensity.
  • Schedule strenuous activities for the coolest parts of the day (typically early morning or late evening).
  • Provide frequent breaks in cool, well-ventilated areas.
  • Encourage use of protective clothing, including wide-brimmed hats and sunscreen.
  • Encourage a "buddy system" for workers to monitor each other for signs of heat-related illness.
  • Monitor workers for signs of distress, such as extremely high body temperature (above 103°F orally), red, hot, and dry skin (no sweat), dizziness, nausea or vomiting, confusion, weakness, seizures, or unconsciousness.
  • Educate workers on symptoms of heat stroke and heat exhaustion and protective measures and encourage workers to report symptoms early.

Animals

During hot weather, it’s very important to make sure your animals are kept comfortable – including pets and service animals. Protect their health by taking precautions:

  • Never leave animals (or people) in a vehicle during warm weather. If you see an animal in a hot vehicle, report it to 911 or the Fairfax County Police non-emergency number at 703-691-2131.
  • Keep walks shorter than usual, take breaks in the shade, and bring water. Urban heat islands may have few trees or parks, so identify shady spots early on.
  • Remember that urban heat islands can have a lot of pavement or asphalt. Walk animals on grass to avoid burning their paws. 
  • Know the symptoms of overheating in animals: excessive panting, difficulty breathing, increased heart rate, drooling, weakness, and even collapse.
  • Bring your animals inside to air conditioning on extremely hot days when possible. If you don’t have air conditioning at home, identify cool places you can go with them.  
     

What Fairfax County is Doing to Help

Fairfax County is working to reduce urban heat islands and help keep you safe in the heat in several ways:

  • Resilient Fairfax – Resilient Fairfax is the plan to help Fairfax County adapt and become more resilient to changing climate-related conditions such as extreme heat, severe storms, and flooding. Since it was adopted by the Board of Supervisors in 2022, the plan is being implemented by an interagency team of over 25 county agencies. Resilient Fairfax includes 48 strategies to create climate-ready communities, adaptive environments, resilient infrastructure and buildings, and integrated action planning. These strategies include enhancements to many of the programs and policies listed below.  
     
  • Heat-related outreach and education – County agencies collaborate to provide heat-related outreach and education to residents through in-person events, webinars, informational materials, and more. Please see Extreme Heat Resources. 
     
  • Heat protocols for athletes and recreation – Fairfax County Public Schools has heat-related protocols in place for outdoor sports and recreation to ensure that students are safe during high temperatures. These include protocols for hydration, practice length, breaks, uniforms and equipment, and types of physical activity permitted for specific temperatures.
     
  • Heat protocols for county employees – Fairfax County also has heat-related protocols for county employees who are outdoor workers. These protocols are currently being updated by an interagency team. 
     
  • Homeless Healthcare Program (FCHD) – The Fairfax County Homeless Healthcare Program ensures that unhoused Fairfax residents receive care for chronic and acute health conditions, have their prescriptions refilled, and are connected to dental and eye care services. During hot months, the program ramps up its street outreach to provide healthcare services and heat-related illness prevention education to unhoused populations. 
     
  • Health in All Policies (FCHD) – Health in All Policies (HiAP) is a strategy to integrate health considerations into policy decisions across other sectors, like transportation or stormwater planning, to improve public health. As part of this approach, proposed revisions to the County’s Comprehensive Policy Plan include new policy guidance promoting climate health, with a significant focus on reducing heat islands by utilizing green infrastructure solutions, particularly in areas of the County more vulnerable to the effects of high heat.
     
  • Cooling Centers – When Fairfax County’s heat plan is activated, cooling centers around the county will be available during normal operating hours for individuals needing relief from the heat. Fairfax County will activate its heat plan when the National Weather Service issues an advisory, watch or warning (usually 24 hours in advance). View heat forecast.
    • Heat Advisory: Issued when the heat index values is expected to reach 105 to 109 degrees within the next 12-24 hours.
    • Extreme Heat Watch: Issued when there is a potential for the heat index to reach or exceed 110 degrees within the next 24-48 hours.
    • Extreme Heat Warning: Issued when the heat index values is expected to reach or exceed 110 degrees within the next 12-24 hours.
       
  • Senior Cool Care Program – The Senior Cool Care Program is a program that helps low-income older citizens in our jurisdiction keep cool during summer months. This program does not provide financial assistance, but it provides additional cooling at home by providing air conditioning units, window air conditioning units or fans for eligible older adults, age 60 and older.

    The program runs May 1 through October 31, 2025. If you are interested in learning more about the program, please call the Aging, Disability & Caregiver Resources Line at 703-324-7948 or visit the Senior Cool Care Program page.
     
  • Cooling Assistance Program – The Cooling Assistance Program helps households manage cooling costs during the hottest months of the year. Assistance includes payment of electric utility bill, cooling equipment repair, purchase of a window or portable A/C unit and/or a one-time payment of an electric security deposit. Program eligibility requires households include individuals who are age 60 or older, 5 or younger, or someone with a disability. 

    Applications for Cooling Assistance are being accepted until August 15, 2025. To apply visit CommonHelp.Virginia.gov, call the Enterprise Customer Service Center at 833-522-5582, or request a paper application by calling DFS at 703-324-7500.
     
  • AC Rescue – This new program provides small air conditioning (AC) equipment for county residents who are unable to receive help from other cooling programs. There are no age or disability requirements, and the program is open year-round to residents who make up to 80% area median income.

    The program is administered by the Office of Environmental and Energy Coordination in partnership with Rebuilding Together. For more information, visit AC Rescue or call 703-324-7262.
     
  • Tree Canopy – Tree canopy is one of Fairfax County’s most effective defenses against urban heat islands. Trees provide shade, reduce pavement and building surface temperatures, and cool the air through evapotranspiration. Land Development Services (LDS) plays a key role in preserving and expanding this critical green infrastructure. Through the site development review process, LDS enforces requirements for tree preservation and replanting, particularly in areas vulnerable to high heat. LDS also guides updates to technical standards and policies that promote the use of native and climate-resilient tree species, helping ensure long-term canopy health and function. By integrating tree canopy goals into land development, LDS supports countywide efforts to reduce localized heat impacts and advance climate adaptation.
     
  • Heat Resilient Design – As part of the Resilient Fairfax plan, the county is implementing heat-resilient design guidelines in various county policies and design guidelines. Heat-resilient design concepts include cool roofs, cool pavements, passive cooling, green infrastructure, building orientation to reduce sun exposure during the hottest months, ventilation options, sufficient natural and architectural shade, and more.
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