What was the worst air-quality day in Bakersfield?

August 22, 2020, when daily PM2.5 reached 158.6 µg/m³ (AQI 234), about 7.2 cigarette-equivalents. It ranks first of 9,578 monitored days since 1999.

What is the highest AQI recorded in Bakersfield?

On the worst day, the daily PM2.5 AQI reached 234 (Very unhealthy). EPA's official metro AQI, which uses the single worst monitor of any pollutant, peaked at 267 on September 8, 2020.

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 Bakersfield get air this bad?

Rarely. The record sits at the far end of 9,578 measured days; Bakersfield averages 12 "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

Bakersfield's worst air quality days

#32 of 100 US metros by worst day · Bakersfield, CA metro area

Based on the available regulatory-monitor record since 1999, August 22, 2020 ranks as Bakersfield's most severe daily PM2.5 day: 158.6 µg/m³ (AQI 234, very unhealthy), about 7.2 cigarettes in a day.

Daily rank: #1
Period of record: Since 1999
Peak daily PM2.5: 158.6 µg/m³
About: 7.2 cigarettes
Status: Finalized

Current conditions on the smoke map → Data through Apr 30, 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 8 EPA monitors in the Bakersfield, CA metro area (CBSA). Days after April 30, 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 267 on September 8, 2020 (defining pollutant PM10).

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 Bakersfield's worst days?

Rank	Date	Daily PM2.5
#1	August 22, 20202-day stretch	158.6 µg/m³
#2	January 5, 20012-day stretch	154.7 µg/m³
#3	November 13, 19992-day stretch	134.8 µg/m³
#4	December 25, 1999	134.1 µg/m³
#5	November 14, 1999	133.9 µg/m³
#6	August 21, 2020	130.2 µg/m³
#7	September 8, 2020	125.4 µg/m³
#8	January 22, 2001	120.4 µg/m³
#9	January 7, 2001	119.4 µg/m³
#10	December 18, 2013	114.9 µg/m³
#11	December 31, 20003-day stretch	112.7 µg/m³
#12	December 30, 2000	111 µg/m³
#13	December 29, 2000	109.6 µg/m³
#14	May 23, 2012	108.4 µg/m³
#15	April 11, 2010	107.8 µg/m³

What caused Bakersfield's worst days?

The event catalog has named 9 episodes affecting Bakersfield, 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.

Wildfire smoke 2020-09-08 Bakersfield wildfire-smoke episode Sep 8, 2020 · 125.4 µg/m³ here , #7 all-time · from Bakersfield, CA
Wildfire smoke 2020-08-19 6-area wildfire-smoke episode Aug 22, 2020 · 158.6 µg/m³ here , #1 all-time · from Bakersfield, CA
Fireworks Fireworks episode, 2017-12-31 through 2018-01-02 Jan 2, 2018 · 100.9 µg/m³ here , #25 all-time
Other Other episode, 2013-12-17 through 2013-12-18 Dec 18, 2013 · 114.9 µg/m³ here , #10 all-time
Dust 2010-04-11 windblown-dust episode affecting Bakersfield, CA Apr 11, 2010 · 107.8 µg/m³ here , #15 all-time
Other San Joaquin Valley particulate-ammonium-nitrate episode Jan 5, 2001 · 154.7 µg/m³ here , #2 all-time · from San Joaquin Valley, California

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

How does it compare?

The record is 3% higher than the next-worst day: 158.6 µg/m³ (August 22, 2020) against 154.7 µg/m³ (January 5, 2001).

How unusual is air like this?

12× a typical day here, at the record

12 days a year, on average, at "unhealthy" or worse

0 µg/m³159 µg/m³

Every measured day near Bakersfield, by daily PM2.5; the record stands far out on the right. 1,001 days at "unhealthy for sensitive groups" or worse, 335 at "unhealthy", 6 at "very unhealthy" (2024 EPA thresholds, across 9,578 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 Bakersfield?: August 22, 2020, when daily PM2.5 reached 158.6 µg/m³ (AQI 234), about 7.2 cigarette-equivalents. It ranks first of 9,578 monitored days since 1999.
What is the highest AQI recorded in Bakersfield?: On the worst day, the daily PM2.5 AQI reached 234 (Very unhealthy). EPA's official metro AQI, which uses the single worst monitor of any pollutant, peaked at 267 on September 8, 2020.
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 Bakersfield get air this bad?: Rarely. The record sits at the far end of 9,578 measured days; Bakersfield averages 12 "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: bakersfield.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: Bakersfield, CA. iaqng.com/records/bakersfield. Data: U.S. EPA AQS and AirNow. Accessed July 26, 2026.