Prescribed fire Likely provisional
Daily PM2.5 peaked at 36.1 µg/m³ near Austin across 1 covered metro home to 2.6 million people.
Counting the extra PM2.5 above each metro's typical day, this event handed the average affected resident ≈ 1.2 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 3.1 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.
Why we think this happened
Contemporaneous Central Texas reporting attributes the exact-window haze to seasonal agricultural burning transported north by southerly winds.
Likely Applicable reporting or a supported inference makes this the best current causal explanation.
Texas Commission on Environmental Quality official
TCEQ reports a preliminary 24-hour PM2.5 concentration of 36.2 ug/m3 at Austin Webberville Road on April 27, 2026. The report validates the observation but does not assign a cause.
Austin-area local reporting corroborates
The April 28 report attributes Central Texas haze to seasonal agricultural burning carried north by southerly winds.
Evidence path
A cause is more convincing when the record connects three things: something happened, the air mass moved toward the region, and local instruments responded. Here is how much of that chain is documented for this event.
Source or mechanism
The April 28 report attributes Central Texas haze to seasonal agricultural burning carried north by southerly winds.
View supporting source ↗Air-mass movement
The retained record does not yet show how air traveled from the proposed source to these metros. A trajectory replay or dated plume analysis belongs here.
Local response
TCEQ reports a preliminary 24-hour PM2.5 concentration of 36.2 ug/m3 at Austin Webberville Road on April 27, 2026. The report validates the observation but does not assign a cause.
Inspect the pollutant and weather signals ↓Event autopsy
Before, during, and after the episode: nearby pollutant monitors and surface-weather stations show what changed. This context tests the “Prescribed fire” explanation; it does not assign the cause by itself.
Austin-Round Rock, TX
Monitor comparison window 2026-04-24 to 2026-04-30
The PM2.5 event remains in the catalog, but the surrounding monitoring record cannot supply a defensible instrument fingerprint for this place and date.
Source: U.S. EPA AirData daily observations and, where available, nearby ASOS/AWOS surface observations. Values are descriptive medians over the retained monitor set; missing measurements remain missing. Transport and source evidence remain separate layers because this instrument pattern does not assign a cause by itself.
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.
Views from the selected metro
Select a metro on the map to see nearby cameras. Where an operator archive reaches the event, drag the divider to compare two moments, adjust either date and time, or play the available event-day frames. Camera imagery is visual context, not an air-quality measurement or proof of smoke.
No useful public camera views are currently available within 80 km of this metro.
| Metro | Peak PM2.5 | Cigarettes, whole event | Peak day | All-time standing |
|---|---|---|---|---|
| Austin-Round Rock, TX | 36.1 µg/m³ | 1.6 | Apr 27, 2026 | #17 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.
Public evidence library
Each card states what a source supports—and what it does not. Official records, research, reporting, community observations, and transparent inferences remain visibly different kinds of evidence.
Austin-area local reporting
The April 28 report attributes Central Texas haze to seasonal agricultural burning carried north by southerly winds.
A retained source supports the attributed cause for the stated place and dates.
Likely Applicable reporting or a supported inference makes this the best current causal explanation.
This episode was grouped from the monitor record by the catalog pipeline and given its cause from the evidence listed above. It has not been individually reviewed and signed off, so its boundaries, cause, and name may change as evidence accumulates. Recent days are preliminary AirNow readings and re-rank once EPA certifies them. Grouping policy common_sense_root_cause_grouping.v2. The cause label reflects the assembled evidence above, not an IAQng detection formula. If it is wrong, tell us.