As the most recent heat dome has tightened its grip across the United States the past few days, scorching more than 90 million people under triple-digit temperatures, another invisible threat is building alongside the heat: polluted air.
From New York City to Cincinnati to Grand Rapids, poor air quality is compounding the dangers of extreme heat. Scientists now warn that these twin environmental hazards—heat and air pollution—are not just co-occurring. They’re actively making each other worse.
Although the worst of this week’s heat may have peaked in some areas, summer is just getting started. With more hot, stagnant days ahead, the conditions that make air pollution so dangerous—like high pressure systems, heat inversions, and wildfire smoke—will remain a serious concern. What we’re experiencing now could be a preview of what’s to come in July, August, and beyond.
A Dangerous Feedback Loop: Heat and Pollution
Extreme heat doesn’t just feel miserable—it actually cooks the air we breathe.
Heat domes, which are massive high-pressure systems that trap hot, stagnant air over large regions, act like atmospheric lids. With little wind to disperse emissions, pollutants like car exhaust, factory fumes, and wildfire smoke accumulate in place, forming what experts call a “chemical soup.”
This process worsens two major types of air pollution:
Ground-Level Ozone: Created when sunlight reacts with pollutants from cars, power plants, and industrial sources, ozone forms close to the ground—right where we breathe. Hot, sunny days supercharge this reaction. The result? Higher concentrations of ozone that irritate the lungs, trigger asthma attacks, and make it harder to breathe, especially for children, seniors, and people with respiratory or cardiovascular conditions.
Particulate Matter (PM2.5 Rising temperatures contribute to more frequent drought conditions and more severe wildfires—both of which drive up levels of harmful fine particulate matter (PM2.5).1 These microscopic particles, smaller than the width of a human hair, come from smoke, dust, and combustion. When inhaled, PM2.5 travels deep into the lungs and even enters the bloodstream, where it can affect nearly every organ system—including the heart, lungs, and brain.
The Health Toll: More Trouble
When heat and air pollution strike together, the health impacts aren’t just additive—they’re multiplied.
A 2023 global study analyzing over 20 million deaths found that mortality rates were significantly higher on days with both extreme heat and poor air quality.2 In the U.S., hospitals are already reporting spikes in asthma attacks, heat exhaustion, and cardiovascular events linked to the ongoing heat wave.
The study revealed a synergistic effect—high pollution makes heat more dangerous, and high heat amplifies the harmful impact of pollution. This deepens scientific concerns about future summers, as climate change is increasing both temperature extremes and air pollution episodes.
Dr. Mary Rice, a pulmonologist at the Harvard T.H. Chan School of Public Health, explains:
Wildfire Smoke: A Growing Threat
Climate change is fueling more frequent and intense wildfires—adding another layer to the pollution crisis. Wildfire smoke is rich in PM2.5 and can also carry toxic compounds from man-made materials like plastics and treated wood. When inhaled, this smoke doesn’t stay local. It travels across state lines and even entire regions, clouding skies and choking air thousands of miles from the source.
In 2018 alone, wildfire smoke was linked to an estimated 12,000 premature deaths in California. As heat domes dry out forests and increase ignition risk, wildfire smoke is becoming a permanent fixture of the summer season.
Why Heat Traps Pollution: The Role of Atmospheric Inversion
Normally, warm air near the Earth’s surface rises and allows polluted air to disperse. But during a heat dome, the air above becomes even hotter, forming a cap that prevents the lower layer from rising—a phenomenon known as temperature inversion. Pollution then gets stuck close to the ground and builds up to dangerous levels.
Urban areas are hit hardest due to the urban heat island effect, where concrete and asphalt absorb and retain more heat. But rural communities are also vulnerable—ozone and PM2.5 can travel far on the wind, bringing dangerous air quality to places with no nearby pollution sources.
How to Stay Safe During a Heat Wave + Air Quality Alert
If your city is under a heat advisory or air quality alert, take these precautions:
🏠 Protect Your Indoor Air
- Close windows and doors during peak pollution hours (usually midafternoon).
- Use a HEPA and activated carbon air purifier—preferably one designed to handle both particulates (like wildfire smoke) and VOCs (from things like car exhaust and chemical cleaners), like the HealthMate Plus.
- Avoid burning candles, using gas stoves, or vacuuming unless your machine has a high-quality air purifier.
These everyday activities can worsen indoor air quality when ventilation is limited.
🌡️ Manage the Heat
- Stay hydrated—drink water regularly, even if you’re not thirsty. Dehydration can creep up on you during extreme heat, and thirst isn’t always a reliable indicator.
- Avoid strenuous activity during the hottest parts of the day, typically between 11 a.m. and 4 p.m.
- Cool down with wet cloths, cold showers, or fans if you don’t have AC. Rest in the shade or in air-conditioned spaces whenever possible.
- Use blackout curtains or thermal blinds to block solar heat gain and keep indoor temperatures more manageable.
📲 Stay Informed
- Track local conditions with AirNow.gov, your state’s EPA site, or a real-time air quality app.
Follow heat alerts and air quality advisories from your local public health department or weather service to know when to stay inside or take extra precautions.
🚸 Check on Vulnerable People
And perhaps most importantly, please do your part to keep an eye on elderly neighbors and vulnerable family members. Older adults, infants, and young children are less able to regulate body temperature and may not express discomfort in time to prevent harm.
People with asthma, heart disease, or mental health conditions are also more likely to suffer complications during extreme heat and poor air quality. Make a point to check in on neighbors, family members, and friends who may need help.
And don’t forget about pets—they rely on us for shade, cool shelter, and plenty of fresh water.
Clean Air Is a Health Essential
As climate change and heat domes reshapes our summers, heat waves and bad air are no longer separate crises. They are linked, dangerous, and increasingly common. But that doesn’t mean you’re powerless.
By taking steps to protect your indoor air and staying informed during extreme weather, you can reduce your risk—and help others do the same.
Because breathing better isn’t just about comfort. It’s about your health.
REFERENCES
1 Cardenas B, Akhtar S, and Elliott B. (2024 September 10). What happens when extreme heat and air pollution collide. World Resources Institute. https://www.wri.org/insights/extreme-heat-air-pollution.
2 Stafoggia M, Michelozzi P, Schneider A,et al. (2023 October 10). Joint effect of heat and air pollution on mortality in 620 cities of 36 countries. Environ Int. 181:108258. doi: 10.1016/j.envint.2023.108258.
3 Brown C and Kelso C. (2025 June 24). Extreme Heat Is Exacerbating Air Pollution, a ‘Double Whammy’ for Health. The New York Times. https://www.nytimes.com/2025/06/24/climate/extreme-heat-pollution-health.html.
