As summer heat intensifies across American cities, the health burden is not falling equally. Black Americans — disproportionately concentrated in the hottest urban neighborhoods, less likely to have home air conditioning, and more likely to live with the chronic conditions that make heat dangerous — are bearing a heavier share of the illness, the hospitalizations, and the deaths.
And that gap is widening.
A January 2026 study published in One Earth projected future heat exposure for every U.S. county through 2100, concluding: "We find that exposure rises everywhere, but gaps widen, especially in the South and among older adults and Black communities." The study found significant racial disparities in urban heat exposure persist in 71 percent of U.S. counties even when adjusting for income.
Why This Matters
Heat is the deadliest weather-related hazard in the United States. In 2023, at least 2,300 death certificates cited excessive heat as a cause of death — a new record. The CDC reported more than 119,000 emergency department visits for heat-related illness in 2023 alone.
The health burden of extreme heat is not abstract. It produces real hospitalizations and deaths, concentrated in specific ZIP codes, specific neighborhoods, and specific demographic groups — in ways that are directly traceable to historical policies of residential segregation, disinvestment, and unequal access to basic protections.
According to KFF, while extreme heat affects everyone, communities of color have higher risks of heat-related mortality than white populations, due to underlying inequities in heat exposure and access to protection.
What We Know So Far
The research on racial heat disparities has reached a consistent and well-documented conclusion across multiple independent data sources.
Urban heat island exposure. According to a comprehensive analysis in One Earth and related peer-reviewed studies, Black residents have the highest average surface urban heat island (SUHI) exposure across all climatic zones — arid, snow, temperate, and equatorial. The urban heat island effect raises daytime air temperatures by up to 7 degrees Fahrenheit in affected areas. Historical patterns of residential segregation, known as redlining, concentrated Black households in neighborhoods with more paved surfaces, less tree cover, and fewer parks — the physical environment that creates and sustains urban heat islands.
Air conditioning access. KFF's analysis of access to home air conditioning found that more than 35 million Americans report living without air conditioning. Brookings Institution research found large Black-white disparities in AC access in multiple major cities — in Detroit, less than 4 percent of white households lack AC, compared to more than 15 percent of Black households. In New York, the gap is nearly 10 percentage points. In Rochester, nearly 30 percent of Black households lack AC versus less than 15 percent of white households.
Chronic disease burden. Research published in PMC documents that Black Americans have higher rates of cardiovascular disease, hypertension, diabetes, and asthma — all conditions that significantly increase the risk of hospitalization or death from extreme heat. A person with hypertension, diabetes, or heart failure does not thermoregulate the same way a healthy person does when temperatures climb.
Where the Disparities Are Worst
The confluence of urban heat, low AC access, and high chronic disease burden is most acute in specific cities and metro areas.
Houston: A 2023 heat wave produced hundreds of heat-related deaths. Houston's predominantly Black and Hispanic neighborhoods in the Fifth Ward, Kashmere Gardens, and Third Ward have long been identified in city heat mapping studies as the hottest and most heat-vulnerable areas in the city.
Phoenix: The Maricopa County Department of Public Health confirmed 645 heat-associated deaths in 2023. Black residents in Maricopa County experience heat-associated mortality at a disproportionate rate.
Atlanta: Fulton County's urban heat island effect is concentrated in predominantly Black south Atlanta neighborhoods, where the Hartsfield-Jackson flight path, industrial land use, and limited tree canopy compound to produce temperatures measurably higher than north Atlanta suburbs.
The 2026 One Earth study specifically identified the South as the region where the widening of heat disparities will be most pronounced over the coming decades.
What Doctors and Experts Say
"We need to be making sure that people have access to air conditioning in their homes," Rachel Licker, principal climate scientist at the Union of Concerned Scientists, told ABC News. "We know that communities of color have disproportionately lower access to air conditioning and the ability to run it. Obviously, that's becoming more and more of an issue as energy bills are increasing right now."
Public health experts consistently point to a compounding effect: when high energy costs prevent low-income households from running air conditioning even when they have it, the protective benefit disappears. Rising electricity costs from climate-driven demand spikes may reduce the real-world AC access rate even as physical ownership remains steady.
KFF's analysis notes that effective heat resilience planning must include equity analysis — identifying which communities have the least protection and targeting resources accordingly.
What the Evidence Shows — and What It Does Not
The data linking urban heat island exposure, reduced AC access, and heat-related mortality by race and income is robust and consistent across multiple independent research teams, methodologies, and geographies. The causal pathway — historical residential segregation → concentrated heat exposure + reduced protection → elevated mortality — is well established.
What is more uncertain is the precise magnitude of the projected widening of disparities, which depends on assumptions about future climate trajectory, tree planting and urban greening investments, AC ownership trends, and electricity affordability. The One Earth projections represent a range of scenarios rather than a single forecast.
Who Faces the Greatest Risk?
The most heat-vulnerable individuals include:
- Black Americans in urban neighborhoods with low tree canopy and high pavement density
- Low-income households without air conditioning or unable to afford to run it
- Adults over 65 with heart disease, hypertension, diabetes, or chronic kidney disease
- People taking medications that impair heat tolerance, including diuretics, beta-blockers, and certain antipsychotics
- Outdoor workers in construction, agriculture, and landscaping — sectors where Black and Hispanic workers are overrepresented
- People without transportation, who cannot easily reach cooling centers when needed
- Incarcerated people, who often lack AC in facilities in hot states
Symptoms and Warning Signs to Watch For
Heat exhaustion — the warning stage before heat stroke — includes:
- Heavy sweating, cold or pale skin
- Fast and weak pulse
- Nausea and weakness
- Muscle cramps
- Fatigue and dizziness
Heat stroke is a medical emergency. Signs include:
- Body temperature above 103°F
- Hot, red, dry, or damp skin
- Rapid, strong pulse
- Confusion or altered consciousness
Call 911 immediately for heat stroke. Move the person to a cooler environment and apply cool water or ice packs to the neck, armpits, and groin while waiting for emergency care.
What You Can Do Now
- Know the cooling center locations in your city before a heat emergency. Most major cities operate cooling centers during extreme heat events; check your local health department or city government website.
- Check on elderly neighbors, family members, and people without air conditioning during heat events — particularly those who live alone.
- If you do not have air conditioning at home, identify your nearest public cooling center — library, community center, mall, or cooling bus — and use it during peak heat hours (10 a.m. to 4 p.m.).
- If you have air conditioning but face high energy bills, contact your local utility company about Low-Income Home Energy Assistance Program (LIHEAP) benefits, which can reduce cooling costs.
- Community organizations and cities can take structural action by planting trees in heat island areas, providing portable AC units to at-risk residents, and including ZIP-code-level heat vulnerability data in emergency response plans.
Cost and Access: What Patients Should Know
LIHEAP provides financial assistance for cooling costs to eligible low-income households. Eligibility and benefit levels vary by state. To apply, contact your local community action agency or state LIHEAP office, or call the National Energy Assistance Referral line at 1-866-674-6327.
Many cities also have programs that provide portable air conditioning units to low-income or elderly residents who qualify. Contact your local health department for information on programs in your city.
What Happens Next
The 2026 summer heat season is underway and expected to be intense across the South and Southwest. Urban heat resilience planning is increasingly being integrated into local climate adaptation plans, but implementation is uneven. Federal climate equity investments from the Inflation Reduction Act had directed funding toward urban greening and cooling in underserved communities; the status of those programs in 2026 depends on ongoing appropriations decisions. MedicalDaily will continue tracking heat-related illness and mortality data through the summer.
The Bottom Line
Extreme heat is the deadliest weather hazard in the United States, and its burden falls unequally. Black Americans face higher heat exposure from urban heat islands, lower rates of home air conditioning, and greater prevalence of conditions that make heat dangerous — and research projects this gap will widen, not close, as temperatures rise. Understanding this disparity is the first step toward addressing it, both in individual communities and in the policies that determine who gets protection and who does not.
References
- ScienceDirect / One Earth — Projected Widening of Sociodemographic Heat Disparities in the United States by End of Century (January 2026)
- KFF — Continued Rises in Extreme Heat and Implications for Health Disparities
- KFF — Disparities in Access to Air Conditioning and Implications for Heat-Related Health Risks
- Brookings Institution — Access to Air Conditioning Is an Urgent Public Health Issue
- PMC — Heat Islands and Chronic Disease: Could African Americans Be More Vulnerable?
- University of Michigan SEAS — Urban Heat Islands and a Climate of Inequities
- ABC News — Why Extreme Heat Endangers More Black, Hispanic, and Indigenous People
