Historical PM2.5 records
Kansas City's worst air quality days
Based on the available regulatory-monitor record since 1999, March 13, 2003 ranks as Kansas City's most severe daily PM2.5 day: 71.4 µg/m³ (AQI 162, unhealthy), about 3.2 cigarettes in a day.
- Daily rank
- #1
- Period of record
- Since 1999
- Peak daily PM2.5
- 71.4 µg/m³
- About
- 3.2 cigarettes
- Latest event
- 1 day, August 2025
- Status
- Finalized
Current conditions on the smoke map → Data through Mar 31, 2026 · page built July 26, 2026
Photo: Stephen Edmonds (CC BY-SA 3.0)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 18 EPA monitors in the Kansas City, MO-KS 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 293 on March 14, 2025 (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 Kansas City's worst days?
| Rank | Date | Daily PM2.5 |
|---|---|---|
| #1 | March 13, 2003 | 71.4 µg/m³ |
| #2 | July 4, 20202-day stretch | 66.6 µg/m³ |
| #3 | March 14, 2025 | 64.7 µg/m³ |
| #4 | August 1, 2025 | 63.8 µg/m³ |
| #5 | September 7, 20232-day stretch | 60.8 µg/m³ |
| #6 | July 4, 2021 | 54 µg/m³ |
| #7 | August 1, 20212-day stretch | 53.5 µg/m³ |
| #8 | September 6, 2023 | 49.2 µg/m³ |
| #9 | August 2, 2021 | 46 µg/m³ |
| #10 | January 31, 2000 | 44.2 µg/m³ |
| #11 | January 2, 2001 | 43.5 µg/m³ |
| #12 | January 15, 2010 | 43 µg/m³ |
| #13 | July 5, 2020 | 42.1 µg/m³ |
| #14 | July 7, 2015 | 41.9 µg/m³ |
| #15 | December 18, 2009 | 41.5 µg/m³ |
What caused Kansas City's worst days?
The event catalog has named 9 episodes affecting Kansas City, 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.
- Fireworks 2026-07-04 fireworks episode affecting Des Moines-West Des Moines, IA, Omaha-Council Bluffs, NE-IA, Kansas City, MO-KS
- Wildfire smoke July 30–August 5, 2025 Midwest Canadian wildfire-smoke episode
- Dust March 14–15, 2025 central U.S. transported-dust episode
- Wildfire smoke 2023 early-September Canadian wildfire-smoke episode
- Wildfire smoke 2021-08-01 3-area wildfire-smoke episode
- Wildfire smoke 2021-03-09 Kansas City wildfire-smoke episode
3 more, plus every named episode and its evidence is in the event catalog.
How does it compare?
The record is 7% higher than the next-worst day: 71.4 µg/m³ (March 13, 2003) against 66.6 µg/m³ (July 4, 2020).
How unusual is air like this?
Every measured day near Kansas City, by daily PM2.5; the record stands far out on the right. 50 days at "unhealthy for sensitive groups" or worse, 5 at "unhealthy", 0 at "very unhealthy" (2024 EPA thresholds, across 9,587 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 Kansas City?
- March 13, 2003, when daily PM2.5 reached 71.4 µg/m³ (AQI 162), about 3.2 cigarette-equivalents. It ranks first of 9,587 monitored days since 1999.
- What is the highest AQI recorded in Kansas City?
- On the worst day, the daily PM2.5 AQI reached 162 (Unhealthy). EPA's official metro AQI, which uses the single worst monitor of any pollutant, peaked at 293 on March 14, 2025.
- 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 Kansas City get air this bad?
- Rarely. The record sits at the far end of 9,587 measured days; Kansas City averages about one "unhealthy" day every 6 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: kansas-city.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: Kansas City, MO-KS. iaqng.com/records/kansas-city. Data: U.S. EPA AQS and AirNow. Accessed July 26, 2026.