NWS alert mirror official
NWS Tucson Dust Storm Warning
The NWS Tucson office issued an exact-date dust-storm warning based on trained-spotter reports.
Dust Likely provisional
2026-07-09 Tucson, AZ dust episode
Daily PM2.5 peaked at 30.5 µg/m³ near Tucson across 1 covered metro home to 1.1 million people. 1 metro 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 ≈ 1.1 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 1.2 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
The basis for “Dust”
Exact-date NWS and Arizona reporting describe blowing dust generated by Tucson-area storms and subsequent particulate impacts.
Likely Applicable reporting or a supported inference makes this the best current causal explanation.
el-balad.com · Jul 12, 2026 corroborates
National Weather Service issues Dust Storm Alert for three Arizona counties
el-balad.com · Jul 13, 2026 corroborates
National Weather Service Issues Dust Storm In Phoenix Warnings Across Three Counties
Evidence path
From source to city
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.
- 1Documented
Source or mechanism
Dust
The NWS Tucson office issued an exact-date dust-storm warning based on trained-spotter reports.
View supporting source ↗ - 2Research gap
Air-mass movement
The transport path has not been reconstructed
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.
- 3Documented
Local response
30.5 µg/m³ near Tucson
EPA monitors recorded the event across 1 metro. The peak daily concentration is roughly 1.4 cigarette-equivalents at the outdoor daily rate.
Inspect the pollutant and weather signals ↓
Event autopsy
What the instruments saw
Before, during, and after the episode: nearby pollutant monitors and surface-weather stations show what changed. This context tests the “Dust” explanation; it does not assign the cause by itself.
Tucson, AZ
Monitor comparison window 2026-07-06 to 2026-07-12
No comparable co-pollutant or weather observations were available.
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.
Measured daily PM2.5 at EPA monitors, as cigarette-equivalents
EPA monitors sit in metro areas, so the colour clusters there. Land between and beyond
them is unmeasured, not clean: this map shows where IAQng has readings, not the extent
of the smoke.
—
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.
Affected metros
| Metro | Peak PM2.5 | Cigarettes, whole event | Peak day | All-time standing |
|---|---|---|---|---|
| Tucson, AZ | 30.5 µg/m³ | 1.4 | Jul 9, 2026 | #6 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
What supports this account
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.
NWS Tucson Dust Storm Warning
NWS alert mirror
The NWS Tucson office issued an exact-date dust-storm warning based on trained-spotter reports.
What it supports
An official source supports the attributed cause for the stated place and dates.
Limit
The warning polygon was east of the Tucson urban core.
What remains uncertain
- The classification is bounded to the retained evidence and does not apportion every source contributing to the daily PM2.5 value.
Status and provenance
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.