What was the worst air-quality day in Little Rock?

March 15, 2025, when daily PM2.5 reached 50.5 µg/m³ (AQI 138), about 2.3 cigarette-equivalents. It ranks first of 9,783 monitored days since 1999.

What is the highest AQI recorded in Little Rock?

On the worst day, the daily PM2.5 AQI reached 138 (Unhealthy for sensitive groups). EPA's official metro AQI, which uses the single worst monitor of any pollutant, peaked at 161 on June 28, 2005.

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 Little Rock get air this bad?

Rarely. The record sits at the far end of 9,783 measured days; Little Rock averages 0 "unhealthy" days a year.

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.

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Historical PM2.5 records

Little Rock's worst air quality days

#97 of 100 US metros by worst day · Little Rock-North Little Rock-Conway, AR metro area

Based on the available regulatory-monitor record since 1999, March 15, 2025 ranks as Little Rock's most severe daily PM2.5 day: 50.5 µg/m³ (AQI 138, unhealthy for sensitive groups), about 2.3 cigarettes in a day.

Daily rank: #1
Period of record: Since 1999
Peak daily PM2.5: 50.5 µg/m³
About: 2.3 cigarettes
Status: Finalized

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

Show

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 6 EPA monitors in the Little Rock-North Little Rock-Conway, AR 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 161 on June 28, 2005 (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.

What were Little Rock's worst days?

Rank	Date	Daily PM2.5
#1	March 15, 2025	50.5 µg/m³
#2	June 24, 20054-day stretch	48.5 µg/m³
#3	June 25, 2005	48.5 µg/m³
#4	June 27, 2020	48.1 µg/m³
#5	September 11, 20052-day stretch	45 µg/m³
#6	September 3, 19992-day stretch	44 µg/m³
#7	June 26, 2005	43.7 µg/m³
#8	October 15, 2024	43.3 µg/m³
#9	June 20, 2001	42.8 µg/m³
#10	October 11, 2024	42.3 µg/m³
#11	September 2, 1999	41.5 µg/m³
#12	September 10, 2005	41.5 µg/m³
#13	September 10, 2002	41.2 µg/m³
#14	June 23, 2005	40.5 µg/m³
#15	October 29, 2005	40.5 µg/m³

What caused Little Rock's worst days?

The event catalog has named 5 episodes affecting Little Rock, 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.

Dust March 14–15, 2025 central U.S. transported-dust episode Mar 15, 2025 · 50.5 µg/m³ here , #1 all-time · from Southwestern United States
Mixed causes 2024-08-01 mixed causes episode affecting Little Rock-North Little Rock-Conway, AR, Memphis, TN-MS-AR Aug 1, 2024 · 39.5 µg/m³ here , #17 all-time
Dust Late-June 2020 Saharan dust plume Jun 27, 2020 · 48.1 µg/m³ here , #4 all-time · from Austin-Round Rock, TX
Wildfire smoke 2007-06-14 wildfire smoke episode affecting Little Rock-North Little Rock-Conway, AR Jun 14, 2007 · 38.1 µg/m³ here , #25 all-time
Wildfire smoke September 2005 central and eastern U.S. western-fire smoke episode Sep 11, 2005 · 45 µg/m³ here , #5 all-time · from Idaho and Montana

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: 50.5 µg/m³ (March 15, 2025) against 48.5 µg/m³ (June 24, 2005).

How unusual is air like this?

4× a typical day here, at the record

0 days at "unhealthy" in Little Rock's record

0 µg/m³51 µg/m³

Every measured day near Little Rock, by daily PM2.5; the record stands far out on the right. 45 days at "unhealthy for sensitive groups" or worse, 0 at "unhealthy", 0 at "very unhealthy" (2024 EPA thresholds, across 9,783 measured days).

Year by year (1999–2026)

Worst single day each year, by the selected measure.

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:

Concentration vs AQI. µg/m³ is the measurement; AQI is a 0 to 500 index derived from it. "330 µg/m³" and "AQI 500" can describe the same air.
Hourly vs NowCast vs daily. An hourly peak, the NowCast rolling estimate apps display, and the full-day average answer different questions; this page ranks full days.
One monitor vs a composite. A single sensor can read far above or below a citywide figure. The measure toggle above shows both framings.
Live vs certified. Real-time feeds get corrected when EPA certifies data months later, which is why recent days here carry a provisional label.

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 Little Rock?: March 15, 2025, when daily PM2.5 reached 50.5 µg/m³ (AQI 138), about 2.3 cigarette-equivalents. It ranks first of 9,783 monitored days since 1999.
What is the highest AQI recorded in Little Rock?: On the worst day, the daily PM2.5 AQI reached 138 (Unhealthy for sensitive groups). EPA's official metro AQI, which uses the single worst monitor of any pollutant, peaked at 161 on June 28, 2005.
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 Little Rock get air this bad?: Rarely. The record sits at the far end of 9,783 measured days; Little Rock averages 0 "unhealthy" days a year.
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: little-rock.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: Little Rock, AR. iaqng.com/records/little-rock. Data: U.S. EPA AQS and AirNow. Accessed July 26, 2026.