Wildfire smoke
May 19-27, 2024 Mexico and Central America fire-smoke episode in Texas
Daily PM2.5 peaked at 57.7 µg/m³ near McAllen across 5 covered metros home to 22 million people. 3 metros placed a top-ten day in their record.
Counting the extra PM2.5 above each metro's typical day, this event handed the average affected resident ≈ 3.2 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 72 million cigarettes. An awareness illustration of outdoor exposure at 22 µg/m³ per cigarette (Berkeley Earth), counting only the event's ranked days; not a medical dose.
Episode peak
-- cigarettes
The smoke map's scale, replayed over this event: the surface interpolates between covered metros' daily records, framed to the affected region. Hover for a reading, click a metro to pin it to the card. Days a monitor did not report draw nothing.
What happened, in the record
TCEQ evidence describes connected May 19-27 transport of smoke from fires in Mexico and Central America across South and Central Texas, with contemporaneous Houston corroboration on May 27. The overlapping focal events are grouped as one regional occurrence. TCEQ evidence describes connected May 19-27 transport of smoke from fires in Mexico and Central America across South and Central Texas, with contemporaneous Houston corroboration on May 27. The overlapping focal events are grouped as one regional occurrence. TCEQ evidence describes connected May 19-27 transport of smoke from fires in Mexico and Central America across South and Central Texas, with contemporaneous Houston corroboration on May 27. The overlapping focal events are grouped as one regional occurrence. TCEQ evidence describes
Sequence: San Antonio (May 21) → McAllen (May 24) → Austin (May 26) → Houston (May 27) → Dallas (May 27)
Affected metros
| Metro | Peak PM2.5 | Cigarettes, whole event | Peak day | All-time standing |
|---|---|---|---|---|
| McAllen-Edinburg-Mission, TX | 57.7 µg/m³ | 11.9 | May 27, 2024 | #3 of its top days |
| San Antonio-New Braunfels, TX | 56.3 µg/m³ | 14.3 | May 27, 2024 | #4 of its top days |
| Houston-The Woodlands-Sugar Land, TX | 43.6 µg/m³ | 2.0 | May 27, 2024 | #19 of its top days |
| Austin-Round Rock, TX | 41.7 µg/m³ | 5.1 | May 27, 2024 | #9 of its top days |
| Dallas-Fort Worth-Arlington, TX | 38.6 µg/m³ | 1.8 | May 27, 2024 | #23 of its top days |
"Cigarettes, whole event" totals a metro's ranked event days at 22 µg/m³ per cigarette: what a person outdoors there breathed across the event, as the illustration. "All-time standing" is where this episode's days sit in each metro's ranked record (worst-area measure, since 1999). Full local context is on each metro's Air Records page.
The evidence
EPA AQS monitor qualifier 20
- AQS PM2.5 qualifier RG — Fire - Mexico/Central America. EPA AQS carries an agency-submitted request-exclusion qualifier (RG, Fire - Mexico/Central America.) on 24 PM2.5 samples in the candidate CBSA on 2024-05-20, identifying wildfire smoke as affecting the samples. A request-exclusion qualifier is an official submitting-agency causal claim, but this endpoint does not establish EPA concurrence.
- AQS PM2.5 qualifier RG — Fire - Mexico/Central America. EPA AQS carries an agency-submitted request-exclusion qualifier (RG, Fire - Mexico/Central America.) on 24 PM2.5 samples in the candidate CBSA on 2024-05-27, identifying wildfire smoke as affecting the samples. A request-exclusion qualifier is an official submitting-agency causal claim, but this endpoint does not establish EPA concurrence.
- AQS PM2.5 qualifier RG — Fire - Mexico/Central America. EPA AQS carries an agency-submitted request-exclusion qualifier (RG, Fire - Mexico/Central America.) on 24 PM2.5 samples in the candidate CBSA on 2024-05-23, identifying wildfire smoke as affecting the samples. A request-exclusion qualifier is an official submitting-agency causal claim, but this endpoint does not establish EPA concurrence.
- AQS PM2.5 qualifier RG — Fire - Mexico/Central America. EPA AQS carries an agency-submitted request-exclusion qualifier (RG, Fire - Mexico/Central America.) on 24 PM2.5 samples in the candidate CBSA on 2024-05-25, identifying wildfire smoke as affecting the samples. A request-exclusion qualifier is an official submitting-agency causal claim, but this endpoint does not establish EPA concurrence.
- AQS PM2.5 qualifier RG — Fire - Mexico/Central America. EPA AQS carries an agency-submitted request-exclusion qualifier (RG, Fire - Mexico/Central America.) on 24 PM2.5 samples in the candidate CBSA on 2024-05-23, identifying wildfire smoke as affecting the samples. A request-exclusion qualifier is an official submitting-agency causal claim, but this endpoint does not establish EPA concurrence.
- AQS PM2.5 qualifier RG — Fire - Mexico/Central America. EPA AQS carries an agency-submitted request-exclusion qualifier (RG, Fire - Mexico/Central America.) on 21 PM2.5 samples in the candidate CBSA on 2024-05-22, identifying wildfire smoke as affecting the samples. A request-exclusion qualifier is an official submitting-agency causal claim, but this endpoint does not establish EPA concurrence.
- AQS PM2.5 qualifier RG — Fire - Mexico/Central America. EPA AQS carries an agency-submitted request-exclusion qualifier (RG, Fire - Mexico/Central America.) on 24 PM2.5 samples in the candidate CBSA on 2024-05-25, identifying wildfire smoke as affecting the samples. A request-exclusion qualifier is an official submitting-agency causal claim, but this endpoint does not establish EPA concurrence.
- AQS PM2.5 qualifier RG — Fire - Mexico/Central America. EPA AQS carries an agency-submitted request-exclusion qualifier (RG, Fire - Mexico/Central America.) on 24 PM2.5 samples in the candidate CBSA on 2024-05-27, identifying wildfire smoke as affecting the samples. A request-exclusion qualifier is an official submitting-agency causal claim, but this endpoint does not establish EPA concurrence.
- AQS PM2.5 qualifier RG — Fire - Mexico/Central America. EPA AQS carries an agency-submitted request-exclusion qualifier (RG, Fire - Mexico/Central America.) on 24 PM2.5 samples in the candidate CBSA on 2024-05-26, identifying wildfire smoke as affecting the samples. A request-exclusion qualifier is an official submitting-agency causal claim, but this endpoint does not establish EPA concurrence.
- AQS PM2.5 qualifier RG — Fire - Mexico/Central America. EPA AQS carries an agency-submitted request-exclusion qualifier (RG, Fire - Mexico/Central America.) on 24 PM2.5 samples in the candidate CBSA on 2024-05-21, identifying wildfire smoke as affecting the samples. A request-exclusion qualifier is an official submitting-agency causal claim, but this endpoint does not establish EPA concurrence.
- AQS PM2.5 qualifier RG — Fire - Mexico/Central America. EPA AQS carries an agency-submitted request-exclusion qualifier (RG, Fire - Mexico/Central America.) on 24 PM2.5 samples in the candidate CBSA on 2024-05-22, identifying wildfire smoke as affecting the samples. A request-exclusion qualifier is an official submitting-agency causal claim, but this endpoint does not establish EPA concurrence.
- AQS PM2.5 qualifier RG — Fire - Mexico/Central America. EPA AQS carries an agency-submitted request-exclusion qualifier (RG, Fire - Mexico/Central America.) on 24 PM2.5 samples in the candidate CBSA on 2024-05-24, identifying wildfire smoke as affecting the samples. A request-exclusion qualifier is an official submitting-agency causal claim, but this endpoint does not establish EPA concurrence.
- +8 more EPA AQS records on file
Agency and publisher pages 2
- Summary of 2022, 2023, and 2024 Exceptional Event Demonstration for Fine Particulate Matter at Harrison, Kleberg, and Travis Counties TCEQ classifies the May 19-20 Kleberg County PM2.5 event as smoke from fires in Mexico/Central America, corroborating the contemporaneous regional South Texas smoke episode.
- Have you noticed the haze in Houston? We have too. Here’s what’s causing it Contemporaneous Houston reporting attributed the haze to smoke from wildfires across Mexico and Central America drifting north into Southeast Texas.
What remains uncertain
- Agency-submitted AQS qualifiers support attribution but do not by themselves establish EPA concurrence.
Status and provenance
Research preview: this record carries research-only status and its boundaries, cause, and name may change as evidence review completes. Grouping policy common_sense_root_cause_grouping.v2. The cause label reflects the assembled evidence above, not an IAQng detection formula.