# Houston, TX Air Quality Index (AQI) Today > Source: https://breathecheck.com/air-quality/us/texas/houston > Go, short outing, or stay in: a three-state verdict for Houston, its own 30-day AQI trend, and why the Ship Channel can spike air quality outside ozone season. That color and number are today's Houston read, nothing more. It decides the porch walk, the Ship Channel commute, or the kid's soccer practice you're weighing right now. This page tracks the air quality Houston actually breathes over the past 30 days, not one headline figure. Skip refreshing it. Set a threshold and [get told when an ozone day starts](/alerts/), rather than checking. ## Houston's last 30 days, not just today One reading won't tell you if today is ordinary or a spike. This chart rebuilds the air quality Houston has seen over the trailing 30 days, from the same hourly AQI feed as the number above. It also carries a running count of **days above AQI 100 in the last 12 months**. IQAir, AccuWeather and aqicn, plus the Texas Commission on Environmental Quality's own monitor grid, all show today's number. None show the shape behind it, over time. A bad Tuesday that clears by Thursday still shows up here, instead of disappearing. ## Why is it hazy in Houston today? Three mechanisms usually explain it: the AQI averages 24 hours so a bad hour gets diluted, wildfire or industrial smoke can sit aloft above the ground-level monitor, or the nearest Texas Commission on Environmental Quality station sits miles from the hazy block. None of that makes the haze fake — it means the number is a one-day average from one location. The AQI is a 24-hour average, so a genuinely bad hour gets diluted by twenty-three calmer ones before it becomes one headline figure. Smoke can sit aloft, a few thousand feet up, above the ground-level monitor that's actually breathing your street's air — it might drift from a wildfire as far off as Canada, or from a nearer industrial release. The coastal plain side of the metro and the refinery corridor side can also read differently depending on which station is closest. Houston also gets a haze source most ozone-dominant metros in this corpus don't: Saharan dust. It's carried across the Atlantic and the Gulf most summers. It shows up as coarse particulate matter (PM10) rather than the finer PM2.5 that wildfire smoke carries — a real, visible haze with a different chemical fingerprint from either smoke or ozone. [Refinery plumes, ship-channel wind, sunlight-cooked ozone](/why-is-the-air-bad-today/) sets out the national version. ![Bar chart of US monthly search volume for “air quality houston” across Aug 2025 – Jul 2026, month by month: 2,900, 3,600, 3,600, 2,400, 2,400, 4,400, 2,400, 1,600, 1,600, 3,600, 2,400, 4,400. The high is 4,400 (Jan 2026, Jul 2026), 1.7 times the median month of 2,650; the low is 1,600 (Mar 2026, Apr 2026). Bars are neutral blue-grey with the peak month in accent blue — search demand, not AQI, so they carry no EPA band colour.](/img/houston/inline-2.webp) *“air quality houston”, DataForSEO, Aug 2025 – Jul 2026. Peak 4,400 (Jan 2026, Jul 2026) against a median month of 2,650. Winter ratio 98% (Nov-Feb mean over Mar-Oct mean). Bars are neutral blue-grey with the peak month in accent blue — never EPA band colours.* ## What is causing the bad air in Houston? Ground-level ozone drives Houston's air quality nearly year-round, not the wintertime smoke that defines northern and mountain metros. Gulf heat and sunlight cook vehicle and industrial exhaust into ozone, spring through fall. The American Lung Association's 2019 report ranked Houston 9th nationally for worst ozone, a weighted average of 22.3 days a year exceeding federal standards. This is a 2019 figure, not a live one — but it names the mechanism correctly. A second, non-seasonal source sits on top of that baseline: the Houston Ship Channel and its petrochemical corridor. It's one of the largest refining concentrations in the country. An Environmental Defense Fund estimate, published in 2020, put the Port of Houston's own smog-forming pollution at roughly 4.1 tons a year. This project hasn't independently verified that figure, and it excludes individual refineries along the Ship Channel. This corridor can spike fine particulate matter (PM2.5), sulfur dioxide or nitrogen dioxide on short notice. That's unrelated to ozone season entirely — a flaring event, a shutdown, a unit upset. We haven't found a specific, dated Houston flaring event described firsthand in the material reviewed here, so we're not naming one. The corridor's contribution is documented at the refinery-count and emissions-estimate level, not as an as-it-happened account. The Houston-Galveston area's own response to a bad forecast is an Ozone Action Day from the Texas Commission on Environmental Quality — a voluntary call to cut vehicle trips and refueling, not an enforced restriction. That's the program in general terms; we haven't sourced TCEQ's own wording for it, so read the day's actual call from TCEQ rather than from us. ## Is the air safe to breathe in Houston today? Houston's worst air runs on summer ozone, cooked by heat and traffic, with whatever the ship channel adds on a still day layered in. There's no trapped valley here the way a mountain city gets one. **Go** on Good or Moderate air. **Short and unloaded**: a lap of the block instead of three. **Don't go** once the color turns red or worse — a Gulf-humid afternoon at that level isn't safer for being flat instead of boxed in. EPA's everyone-warning starts at 151, Unhealthy. 201 to 300, Very Unhealthy, escalates that same warning rather than adding a new group. Past roughly 200, the outing doesn't happen, industrial source or not. ## What AQI should you stay inside? Nobody here agrees on one number. A runner on r/Marathon_Training: "I'll run in up to 110 because...error bars." An asthmatic runner puts it at a hard 60, from 156 logged runs against AQI. Past it, "my lungs struggle regardless of how well I've trained," EPA's own 100-unhealthy line notwithstanding. Their success rate drops from 87% to 42% to 12% across the under-50, 50-70, and above-70 bands. Parents land somewhere near 100. ![The EPA AQI scale for Houston in six colour bands, each segment as wide as its range: Good 0-50 green, Moderate 51-100 yellow, Unhealthy for Sensitive Groups 101-150 orange, Unhealthy 151-200 red, Very Unhealthy 201-300 purple, Hazardous 301-500 maroon. Beneath, the 0-150 stretch is enlarged to mark three cutoffs quoted on this page: 60 for one asthmatic runner after a 156-run log, about 100 where a parent calls off the outing, and 110 for one r/Marathon\_Training runner.](/img/houston/inline-1.webp) *EPA AirNow's own colours and breakpoints, segment width proportional to the AQI range. The three marks are individual reported cutoffs quoted on this page, not EPA guidance.* A Gulf-humidity ozone afternoon and a wildfire-smoke day pull that table down by different amounts. Smoke goes further — about one EPA band past whatever heat already added. In EPA's scheme [101–150 is Unhealthy for Sensitive Groups](/aqi/), an attributed classification rather than a personal call. No Texas rule sets a school or daycare AQI threshold, at least none this project can confirm. Washington and Minnesota are the two states that have. [The states with a written daycare threshold](/daycare-air-quality-policy/) has both. Go with a portable HEPA purifier, or build a Corsi-Rosenthal box — around $130 got one community member a 12x14 bedroom's worth. A whole-house MERV-13 filter needs a licensed tech to check the system's static pressure first, especially in humid-climate ductwork. [The MERV question, answered without the sales pitch](/indoor/) goes further. ## Why our number may not match what you are seeing and smelling The mismatch between Houston's sky and its AQI number runs both directions. A hazy sky with a fine-reading number is usually 24-hour averaging, or smoke sitting aloft above street level. A clear, ordinary-looking day with a climbing number is ground-level ozone at work. Houston's dominant pollutant most of the year is invisible and odorless. It peaks on the same hot, sunny, low-wind afternoons that look like perfect outdoor weather. That's exactly why the reading and the sky disagree most, on the days Houston looks its best. That's the monitoring station feeding today's reading, its distance from the metro centroid, and the nearby PurpleAir sensor count. A station miles from where you're standing under-reports whichever side of the metro sits farthest from it. Often that's the Ship Channel side, where industrial and residential air can read differently from what a downtown or west-side monitor shows. [Why a downtown monitor and a Ship Channel monitor disagree](/methodology/) covers that split. ## Why Houston's air quality runs on ozone, not inversion Houston runs on ozone, not inversion. It never gets the cold-air-pool lid that traps pollution over Salt Lake City, Denver or Boise each winter. It's too flat, too warm and too close to sea level for that lid to form. Its ozone instead builds through the warm months, roughly spring through fall, driven by heat and sunlight rather than a trapped, stagnant air mass. AQI aggregates PM2.5 and ozone into one number. That's why [Denver's number can look fine while the ozone is the problem](/air-quality/us/colorado/denver). The same mechanism runs under [Atlanta's own ozone season](/air-quality/us/georgia/atlanta) and [Phoenix's summer ozone spikes](/air-quality/us/arizona/phoenix), and under Los Angeles's smog longest of all. Houston's own addition to that pattern is the port and petrochemical corridor along the Ship Channel. That's a source class the ozone-only metros don't share. [Long Beach carries the same port-and-industrial mix](/air-quality/us/california/long-beach), and so does [Oakland, on its own stretch of bay](/air-quality/us/california/oakland). The air quality Houston reports is one number for a metro that runs a refinery corridor and a residential suburb at once. The AQI hands you a citywide average, not a reading for either one specifically. ## FAQ ### What's the air quality forecast for Houston tomorrow? Ozone can build or clear within a single day depending on wind off the Gulf. Treat it as a direction, not a lock, and check back the morning of. ### What's the UV index in Houston today? UV runs on its own scale, separate from AQI. Houston's low latitude keeps UV high most of the year, so a good AQI reading is no reason to skip sunscreen. ### Who has the worst air quality in the US right now? See [how Houston ranks today](/) against every tracked city. The air quality Houston reports moves hardest during summer ozone season and during an active Ship Channel or wildfire smoke event. ### Is today an Ozone Action Day in Houston? The Texas Commission on Environmental Quality calls an Ozone Action Day when ozone is forecast to run high across the Houston-Galveston area. It's a voluntary call to cut vehicle trips and refueling, not an enforced restriction.