What the 4th of July Looks Like on the PurpleAir Map

by Amanda Hawkins

Screenshot from the PurpleAir map at 10:09 PM MDT on July 4, 2026.

The 4th of July is, by some measures, the single worst night of the year for fine-particle air pollution across the United States. The image above is a PurpleAir mobile-app screenshot from 10:09 PM MDT on July 4, 2026, showing 10-minute US EPA PM2.5 (AQI) readings. Hundreds of sensors were above 100 (unhealthy for sensitive groups), dozens crossed 300 (hazardous), and a handful of spot readings climbed well over 1,000. The map looks like a wildfire smoke event compressed into a few hours, from coast to coast, with neighborhood-level spikes that rivaled what the West has been seeing from active fires this summer.

A Coast-to-Coast Spike

A 2015 study by NOAA researchers Dian Seidel and Abigail Birnbaum, published in Atmospheric Environment, analyzed 315 EPA air quality sites from 1999 through 2013 and found that average PM2.5 levels rose 42% between 9 and 11 PM local time on July 4, with the elevated readings lingering well into the morning of July 5. That number is a national average. In neighborhoods near professional displays or backyard fireworks, the local spike can be many times larger.

The PurpleAir map shows the same pattern in real time. Sensors near professional displays, beach gatherings, and backyard fireworks record sudden, steep climbs in PM2.5. As the smoke spreads and settles, the spike broadens across whole metro areas. By the morning of July 5, levels are often still elevated, especially in low-lying valleys where overnight inversions trap the smoke close to the ground.

The pattern was consistent across the country: a few sensors lit up around dusk, more as it got darker, a peak between roughly 10 PM and midnight, then a slow tail through the next morning.

What Is in Fireworks Smoke

Fireworks PM2.5 is not the same as wildfire PM2.5. The colors and effects come from specific metal compounds that end up in the fine particles drifting downwind:

  • Strontium (red)
  • Barium (green)
  • Copper (blue)
  • Aluminum and magnesium (bright white and silver)
  • Antimony (glitter effects)
  • Titanium (sparks)

Studies of fireworks fallout have measured elevated airborne concentrations of strontium, barium, and other metals for hours after a major display. Most fireworks also use perchlorates as oxidizers, which can persist in nearby surface water.

For comparison, wildfire PM2.5 is mostly organic carbon, elemental carbon, and a smaller fraction of crustal material. Both are fine particles, both can be inhaled deep into the lungs, but the chemistry is different and the heavy-metal load on the 4th is one of the year’s unusual exposures.

Who Is Most Affected

The same groups at higher risk from wildfire smoke are at higher risk from fireworks PM2.5: children, older adults, pregnant people, anyone with asthma, COPD, heart disease, diabetes, or chronic kidney disease, immunocompromised individuals, and outdoor workers. See Wildfire Smoke and Sensitive Groups for the full list and the reasoning.

A few groups deserve a specific note for the 4th:

  • People with asthma: The fast climb of PM2.5 over a couple of hours is exactly the kind of trigger that sends people to the ER. Keep rescue inhalers in reach and follow your action plan.
  • People with heart conditions: Acute PM2.5 spikes are associated with elevated risk of heart attack and arrhythmia within hours of exposure, not just over the long term.
  • Veterans with PTSD: Less about the air and more about the noise, but worth being aware of in your community.
  • Pets: Dogs and cats breathe the same air you do. Short-nosed breeds (bulldogs, pugs, Persians) and animals with existing respiratory issues are most at risk. Keeping them inside with windows closed protects both their lungs and their nerves.

When Fireworks Meet Fire Season

In 2026, the 4th of July arrived against a backdrop of an unusually active early fire season across the West, and two states in particular made the fireworks-vs-fire tension unavoidable.

Utah. On June 25, Governor Spencer Cox declared a state of emergency and issued an executive order that gave the state forester authority to prohibit personal fireworks statewide through July 5, including within municipal boundaries, in response to historic drought and hundreds of active wildfires that had exhausted firefighting resources. The Cottonwood Fire in southern Utah grew past 112 square miles by late June and was the largest active wildfire in the US at that time. The Iron Fire, Bonneville Fire, and other blazes continued burning as the holiday approached. State officials noted that more than 75 percent of Utah’s 2026 wildfires have been human-caused, and the National Weather Service office in Salt Lake City issued its first-ever “Particularly Dangerous Situation” warning across five counties, a rare alert originally developed for tornado conditions.

Colorado. Air quality along the Front Range and in southern Colorado has been degraded for weeks. As of early July, at least six major fires were active: the Ferris Fire in the San Juan National Forest, the Gold Mountain Fire near Ouray, the Willow Fire near Leadville, the Snyder Fire west of Fruita, and the Aspen Acres and Sheep Mountain fires in southern Colorado. Pueblo public health officials issued an air quality advisory on July 1 as smoke pushed AQI into the unhealthy range southwest of Pueblo West. The state’s Air Quality Advisory for Wildfire Smoke was extended through the morning of July 6, and the Front Range was under an Ozone Action Day the same day.

Layered on top of an already-elevated baseline, fireworks pile on. In communities already breathing wildfire smoke, a neighborhood at moderate AQI from drifting smoke can spike into unhealthy or hazardous range within minutes once the fireworks start. Where fireworks were banned or postponed, the local PurpleAir spike was smaller. Where they went ahead as usual, sensors captured the same red-and-purple pattern shown in the map above.

Heat is the other risk multiplier. July 4 frequently falls during the year’s peak heat, which means people are outside more, hydrated less, and breathing harder. Add fireworks smoke to that and even healthy adults can feel it the next day.

What to Do Next Year

The fireworks themselves are not going anywhere, so the goal is to manage exposure:

  • Check the PurpleAir map on the night of July 4 and again the morning of July 5. Watch the trend for your neighborhood.
  • Close windows before fireworks start and keep them closed overnight.
  • Run a HEPA cleaner or a DIY box-fan filter in the room where you sleep. Set it to high before the show starts.
  • Watch displays from a distance. Standing directly downwind of a professional show, or in the middle of a neighborhood barrage, is the worst place for sensitive lungs.
  • Keep pets inside with white noise or a TV running. Close their windows too.
  • If you have asthma, COPD, or heart disease, keep medications close and follow your action plan. Symptoms that would prompt a doctor call on a smoky wildfire day should prompt one on the 4th too.

A Final Note

The PurpleAir community map exists because regular people put sensors on their porches and rooftops. On the night of the 4th, those same sensors capture a national event in real time.

Independence Day is worth celebrating. So is being able to breathe well the next day.

Wildfire Smoke and Sensitive Groups · What’s Actually in Wildfire Smoke · Preparing for Wildfires · Active Wildfires Across the West: A June 2026 Update

Monitor current conditions on the PurpleAir map or with an air quality monitor at home.

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