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Historical PM2.5 records

Austin's worst air quality days

#91 of 100 US metros by worst day · Austin-Round Rock, TX metro area

Based on the available regulatory-monitor record since 1999, June 27, 2020 ranks as Austin's most severe daily PM2.5 day: 60.3 µg/m³ (AQI 154, unhealthy), about 2.7 cigarettes in a day.

Daily rank
#1
Period of record
Since 1999
Peak daily PM2.5
60.3 µg/m³
About
2.7 cigarettes
Status
Finalized

Current conditions on the smoke map → Data through Mar 31, 2026 · page built July 26, 2026

Photo: LoneStarMike (CC BY 3.0)
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The worst-hit part of the metro: its highest credible monitor each day.
How this is measured sources, the daily measure, and what this ranking is not

Source. Daily PM2.5 from the U.S. EPA Air Quality System (AQS) , back to 1999, across 5 EPA monitors in the Austin-Round Rock, TX metro area (CBSA). Days after March 31, 2026 are preliminary AirNow readings, marked provisional, and re-rank once EPA certifies them (usually the following spring).

The daily measure. "Worst area" is the metro's highest credible monitor each day, with lone bad-monitor spikes dropped (the raw single-monitor max before that filter is in the data but not charted). "Metro average" averages every monitor. The unit choice re-reads the same value as µg/m³, cigarette-equivalents (PM2.5 ÷ 22, Berkeley Earth, an illustration rather than a medical reading), or the EPA 2024 PM2.5 AQI.

Official AQI. EPA's reported metro AQI uses the single worst monitor of any pollutant, so it can run higher than the values here. The highest official daily AQI among the ranked days is 177 on September 13, 2002 (defining pollutant Ozone).

What this ranking is not. It does not attribute days to wildfire smoke: a high-PM2.5 day can be dust, fireworks, an inversion, or industry. The wildfire-smoke event ranking below arrives with a published attribution method.

Austin's monitoring record is thinner than most, 5,385 days since 1999, with gaps between them. The ranking is real, but treat it as indicative rather than a complete accounting.

What were Austin's worst days?

RankDateDaily PM2.5
#1 June 27, 2020 60.3 µg/m³
#2 January 1, 2000 58 µg/m³
#3 September 13, 20023-day stretch 53 µg/m³
#4 May 8, 2024 51.8 µg/m³
#5 September 14, 2002 49.7 µg/m³
#6 September 12, 2002 48.6 µg/m³
#7 January 1, 2017 47.1 µg/m³
#8 January 1, 2023 44.1 µg/m³
#9 May 27, 2024 41.7 µg/m³
#10 January 1, 2019 41 µg/m³
#11 April 2, 2025 39.8 µg/m³
#12 March 15, 2025 38.9 µg/m³
#13 July 16, 2018 38.3 µg/m³
#14 June 16, 2022 37.4 µg/m³
#15 July 31, 2024 37.4 µg/m³

What caused Austin's worst days?

The event catalog has named 12 episodes affecting Austin, each resolved to a cause only where retained evidence supports it: EPA monitor qualifiers, NWS alerts, agency statements, and reporting. The ranking above stays cause-neutral; this is where the causes live.

6 more, plus every named episode and its evidence is in the event catalog.

How does it compare?

The record is 4% higher than the next-worst day: 60.3 µg/m³ (June 27, 2020) against 58 µg/m³ (January 1, 2000).

How unusual is air like this?

6× a typical day here, at the record
1 in 14 years, roughly, sees an "unhealthy" day here
1 µg/m³60 µg/m³

Every measured day near Austin, by daily PM2.5; the record stands far out on the right. 20 days at "unhealthy for sensitive groups" or worse, 2 at "unhealthy", 0 at "very unhealthy" (2024 EPA thresholds, across 5,385 measured days).

Year by year (1999–2026)

Worst single day each year, by the selected measure.

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Why did reported numbers differ?

During a major event, AirNow, weather apps, news reports, and neighborhood monitors can all show different figures at the same moment. All of them can be right:

What about indoors?

Citywide monitors can tell you what happened outside. They cannot tell you what happened inside a particular home, school, or facility: filtration, ventilation, and building operation decide that. During and after days like the ones above, outdoor particles become an indoor load question.

Check current conditions and the next clean-air window → Estimate recent filter load where you are →

Common questions

What was the worst air-quality day in Austin?
June 27, 2020, when daily PM2.5 reached 60.3 µg/m³ (AQI 154), about 2.7 cigarette-equivalents. It ranks first of 5,385 monitored days since 1999.
What is the highest AQI recorded in Austin?
On the worst day, the daily PM2.5 AQI reached 154 (Unhealthy). EPA's official metro AQI, which uses the single worst monitor of any pollutant, peaked at 177 on September 13, 2002.
Were these days caused by wildfire smoke?
This page ranks measured PM2.5 without assigning a cause: a high day can be smoke, fireworks, dust, an inversion, or industry. A separate wildfire-smoke event ranking, using a published attribution method with its version disclosed, is the next layer of this catalog.
How often does Austin get air this bad?
Rarely. The record sits at the far end of 5,385 measured days; Austin averages about one "unhealthy" day every 14 years.
Why did different apps show different numbers that day?
Concentration (µg/m³) and AQI are different scales; hourly, NowCast, and daily values answer different questions; a single monitor differs from a citywide composite; and live feeds get revised when EPA certifies data. This page uses the certified daily record, with the provisional tail labeled.

Data and citation

Ranked days for both measures are downloadable, with units and status flags: austin.csv. Source: U.S. EPA Air Quality System (AQS) daily PM2.5, with preliminary AirNow readings for the uncertified tail. Cite as:

IAQng Air Records: Austin, TX. iaqng.com/records/austin. Data: U.S. EPA AQS and AirNow. Accessed July 26, 2026.