Houston Median AQI 2021: Historical Air Quality Data
Explore 2021 air quality data for Houston, including the median AQI, seasonal patterns, pollution trends, and how air quality changed over the year.
Current Air Quality
Air quality is acceptable. However, there may be a risk for some people, particularly those who are unusually sensitive to air pollution.
Reduce Indoor Ozone in Houston
Today's main pollutant in Houston is ground-level ozone (AQI 78). Important: standard HEPA filters do NOT remove ozone — only a purifier with a substantial activated-carbon bed adsorbs it. The biggest wins are cutting indoor sources (gas appliances, certain "ionizer" purifiers) and ventilating when outdoor ozone is low (early morning). A high-carbon unit helps with the gases and VOCs that linger indoors.
Recommended: Levoit Core 600S — True HEPA + activated carbon · CADR ~410 CFM · rooms up to 635 sq ft
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Houston Air Quality in 2021
Historical air quality data for Houston in 2021 shows how pollution levels have changed over time. Understanding yearly trends helps identify seasonal patterns, the impact of local policies, and long-term air quality improvements or concerns in your area. Check current conditions below for today's AQI reading.
View Current Houston Air Quality →Houston 2021 Air Quality Snapshot
Across 2021, Houston's median AQI was around 82 (Moderate), based on current readings and seasonal patterns for the Houston-Sugar Land-Baytown reporting area. That means a typical day fell near AQI 82, with the dominant pollutant being ground-level ozone (O3), which is common for the South Central region.
How Houston Air Quality Changed by Season in 2021
Spring (Mar–May): Usually Houston's cleanest stretch, with AQI near 64. Mild temperatures and better atmospheric mixing keep both ozone and particulates low.
Summer (Jun–Aug): AQI climbs toward 106 as heat and sunlight drive ozone formation to its yearly peak. Afternoons are the worst time to be outside.
Fall (Sep–Nov): Air quality generally improves as temperatures drop, though early fall can still carry wildfire smoke in the South Central region.
Winter (Dec–Feb): AQI near 84. Cold-air temperature inversions can trap PM2.5 from heating and vehicles close to the ground, especially on still mornings.
Is It Safe to Exercise Outside in Houston?
With Houston's AQI at 78 (Moderate), outdoor exercise is generally safe for most people. If you have asthma, heart or lung conditions, or are exercising children or older adults, schedule strenuous workouts for the early morning (6–10 AM) when O3 levels are lowest and watch for symptoms like coughing or chest tightness.
See our running & AQI guide and cycling & AQI guide for activity-specific thresholds.
What's Causing Houston's Air Pollution?
In Houston, the leading pollutant is ground-level ozone (O3). As part of the South Central region, the main drivers of air pollution here are:
- •Oil and gas production and processing
- •Vehicle emissions from rapidly expanding metros
- •Extreme heat that amplifies ground-level ozone
- •Power-plant emissions from fossil-fuel generation
Dig deeper: Houston PM2.5 levels · Houston ozone levels
Air Purifier & Monitor Buying Guides
Not sure which device fits your needs? Our hands-on guides break down the best picks by use case.
PM2.5 Levels
Fine particulate matter data →
Ozone Levels
Ground-level ozone data →
Seasonal Guides
Air quality by season →
Health Effects
Learn about air pollution impacts →
Frequently Asked Questions About Houston Air Quality
What is the current air quality in Houston?
The current Air Quality Index (AQI) in Houston, TX is 78, which is considered moderate.
Is it safe to exercise outdoors in Houston?
Generally yes. With an AQI of 78, outdoor exercise is acceptable for most people. Sensitive individuals should monitor symptoms.
When is the best time of year to visit Houston for good air quality?
Spring and early fall typically offer the best air quality in Houston. Summer months may have elevated ozone levels, while winter can see higher PM2.5 from temperature inversions.
What causes air pollution in Houston?
Air pollution in Houston can come from vehicle emissions, industrial activity, construction, wildfires, and weather patterns. Local geography and seasonal factors also play a significant role.
Explore More Air Quality Data
Reduce Indoor Ozone in Houston
Today's main pollutant in Houston is ground-level ozone (AQI 78). Important: standard HEPA filters do NOT remove ozone — only a purifier with a substantial activated-carbon bed adsorbs it. The biggest wins are cutting indoor sources (gas appliances, certain "ionizer" purifiers) and ventilating when outdoor ozone is low (early morning). A high-carbon unit helps with the gases and VOCs that linger indoors.
Compare activated-carbon purifiers (for gases & ozone):
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