What was the worst air-quality day in Deltona?

May 9, 2007, when daily PM2.5 reached 114.3 µg/m³ (AQI 192), about 5.2 cigarette-equivalents. It ranks first of 4,881 monitored days since 1999.

What is the highest AQI recorded in Deltona?

On the worst day, the daily PM2.5 AQI reached 192 (Unhealthy). EPA's official metro AQI, which uses the single worst monitor of any pollutant, peaked at 192 on May 9, 2007.

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 Deltona get air this bad?

Rarely. The record sits at the far end of 4,881 measured days; Deltona averages about one "unhealthy" day every 28 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.

← All 100 US metros ranked

Historical PM2.5 records

Deltona's worst air quality days

#48 of 100 US metros by worst day · Deltona-Daytona Beach-Ormond Beach, FL metro area

Based on the available regulatory-monitor record since 1999, May 9, 2007 ranks as Deltona's most severe daily PM2.5 day: 114.3 µg/m³ (AQI 192, unhealthy), about 5.2 cigarettes in a day.

Daily rank: #1
Period of record: Since 1999
Peak daily PM2.5: 114.3 µg/m³
About: 5.2 cigarettes
Latest event: 1 day, February 2026
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 1 EPA monitor in the Deltona-Daytona Beach-Ormond Beach, FL 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 192 on May 9, 2007 (defining pollutant PM2.5).

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.

Deltona's monitoring record is thinner than most, 4,881 days since 1999, with gaps between them. The ranking is real, but treat it as indicative rather than a complete accounting.

Latest major event February 2026 One ranked day, Feb 3, 2026, peaking at 36.7 µg/m³, #6 all-time. See where it ranks ↓

What were Deltona's worst days?

Rank	Date	Daily PM2.5
#1	May 9, 2007	114.3 µg/m³
#2	September 30, 1999	52.2 µg/m³
#3	September 16, 2005	43.6 µg/m³
#4	October 3, 20233-day stretch	42.6 µg/m³
#5	May 3, 2007	40.8 µg/m³
#6	February 3, 2026	36.7 µg/m³
#7	August 26, 2007	35.3 µg/m³
#8	June 12, 2001	31.7 µg/m³
#9	October 2, 2023	30.6 µg/m³
#10	May 18, 2007	29.7 µg/m³
#11	October 18, 2000	29.2 µg/m³
#12	July 23, 2004	29.1 µg/m³
#13	February 26, 1999	28.5 µg/m³
#14	October 4, 2023	28.2 µg/m³
#15	July 19, 2002	27.1 µg/m³

What caused Deltona's worst days?

The event catalog has named 9 episodes affecting Deltona, 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 2023 early-October Canadian wildfire-smoke episode Oct 3, 2023 · 42.6 µg/m³ here , #4 all-time · from Canada
Prescribed fire 2022-03-04 Deltona-Daytona Beach-Ormond Beach, FL prescribed-fire smoke episode Mar 4, 2022 · 24 µg/m³ here , #22 all-time
Wildfire smoke 2007-08-26 wildfire smoke episode affecting Deltona-Daytona Beach-Ormond Beach, FL Aug 26, 2007 · 35.3 µg/m³ here , #7 all-time
Wildfire smoke 2007-05-17 wildfire smoke episode affecting Jacksonville, FL, Deltona-Daytona Beach-Ormond Beach, FL May 18, 2007 · 29.7 µg/m³ here , #10 all-time
Wildfire smoke 2007 Georgia-Florida wildfire-smoke transport episode May 9, 2007 · 114.3 µg/m³ here , #1 all-time · from Ware County, Georgia and northern Florida
Wildfire smoke 2007-05-03 wildfire smoke episode affecting Deltona-Daytona Beach-Ormond Beach, FL, Jacksonville, FL May 3, 2007 · 40.8 µg/m³ here , #5 all-time

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

How does it compare?

The record is 2.2× the next-worst day: 114.3 µg/m³ (May 9, 2007) against 52.2 µg/m³ (September 30, 1999).

How unusual is air like this?

16× a typical day here, at the record

1 in 28 years, roughly, sees an "unhealthy" day here

0 µg/m³114 µg/m³

Every measured day near Deltona, by daily PM2.5; the record stands far out on the right. 6 days at "unhealthy for sensitive groups" or worse, 1 at "unhealthy", 0 at "very unhealthy" (2024 EPA thresholds, across 4,881 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 Deltona?: May 9, 2007, when daily PM2.5 reached 114.3 µg/m³ (AQI 192), about 5.2 cigarette-equivalents. It ranks first of 4,881 monitored days since 1999.
What is the highest AQI recorded in Deltona?: On the worst day, the daily PM2.5 AQI reached 192 (Unhealthy). EPA's official metro AQI, which uses the single worst monitor of any pollutant, peaked at 192 on May 9, 2007.
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 Deltona get air this bad?: Rarely. The record sits at the far end of 4,881 measured days; Deltona averages about one "unhealthy" day every 28 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: daytona.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: Deltona, FL. iaqng.com/records/daytona. Data: U.S. EPA AQS and AirNow. Accessed July 26, 2026.