Wildfire smoke EPA monitor flag
Daily PM2.5 peaked at 158.6 µg/m³ near Bakersfield across 6 covered metros home to 12 million people. 1 metro recorded their worst day on record; 3 placed a top-ten day.
Counting the extra PM2.5 above each metro's typical day, this event handed the average affected resident ≈ 11.4 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 137 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
Supplied qualified evidence supports wildfire-smoke as the root cause. The grouping includes only events linked by explicit shared episode evidence; otherwise this remains a single-event episode.
EPA monitor flag EPA attached an exceptional-event qualifier to the affected samples. The agency flagged the measurement itself; no separate agency record describes the event.
U.S. EPA Air Quality System and the submitting air monitoring agency · Aug 23, 2020 official
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 215 PM2.5 samples in the candidate CBSA on 2020-08-23, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
U.S. EPA Air Quality System and the submitting air monitoring agency · Aug 22, 2020 official
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 1 PM2.5 sample in the candidate CBSA on 2020-08-22, identifying wildfire smoke as affecting the sample. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
U.S. EPA Air Quality System and the submitting air monitoring agency · Aug 23, 2020 official
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 24 PM2.5 samples in the candidate CBSA on 2020-08-23, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
See every retained source and limitation ↓
Sequence: San Francisco (Aug 19) → San Jose (Aug 19) → Sacramento (Aug 20) → Stockton (Aug 20) → Bakersfield (Aug 21) → Fresno (Aug 21)
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
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 215 PM2.5 samples in the candidate CBSA on 2020-08-23, identifying wildfire smoke as affecting the samples. An informational qualifier is an official…
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
EPA monitors recorded the event across 6 metros. The peak daily concentration is roughly 7.2 cigarette-equivalents at the outdoor daily rate.
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 “Wildfire smoke” explanation; it does not assign the cause by itself.
Bakersfield, CA
Monitor comparison window 2020-08-18 to 2020-08-26 · PM2.5 target: Bakersfield-California
150% above nearby days
About the same as surrounding days
47% higher than surrounding days
150% higher than surrounding days
47% higher than surrounding days
104% higher than surrounding days
17% higher than surrounding days
33% higher than surrounding days
About the same as surrounding days
About the same as surrounding days
About the same as surrounding days
About the same as surrounding days
Fresno, CA
Monitor comparison window 2020-08-18 to 2020-08-26 · PM2.5 target: Huron
66% above nearby days
22% lower than surrounding days
47% higher than surrounding days
66% higher than surrounding days
47% higher than surrounding days
58% higher than surrounding days
17% higher than surrounding days
33% higher than surrounding days
About the same as surrounding days
19% higher than surrounding days
About the same as surrounding days
About the same as surrounding days
22% lower than surrounding days
San Francisco-Oakland-Hayward, CA
Monitor comparison window 2020-08-16 to 2020-08-27 · PM2.5 target: Livermore
21% above nearby days
18% lower than surrounding days
21% higher than surrounding days
18% lower than surrounding days
15% higher than surrounding days
About the same as surrounding days
About the same as surrounding days
5% lower than surrounding days
San Jose-Sunnyvale-Santa Clara, CA
Monitor comparison window 2020-08-16 to 2020-08-27 · PM2.5 target: San Jose - Knox Avenue
41% above nearby days
About the same as surrounding days
30% higher than surrounding days
41% higher than surrounding days
30% higher than surrounding days
31% higher than surrounding days
8% higher than surrounding days
About the same as surrounding days
About the same as surrounding days
About the same as surrounding days
About the same as surrounding days
About the same as surrounding days
Sacramento--Roseville--Arden-Arcade, CA
Monitor comparison window 2020-08-16 to 2020-08-27 · PM2.5 target: Lincoln-2885 Moore Road
116% above nearby days
10% lower than surrounding days
20% higher than surrounding days
116% higher than surrounding days
20% higher than surrounding days
28% higher than surrounding days
6% higher than surrounding days
7% higher than surrounding days
18% higher than surrounding days
About the same as surrounding days
About the same as surrounding days
About the same as surrounding days
10% lower than surrounding days
Stockton-Lodi, CA
Monitor comparison window 2020-08-16 to 2020-08-27 · PM2.5 target: Tracy-Airport
196% above nearby days
25% lower than surrounding days
82% higher than surrounding days
196% higher than surrounding days
82% higher than surrounding days
95% higher than surrounding days
22% higher than surrounding days
About the same as surrounding days
8% lower than surrounding days
About the same as surrounding days
About the same as surrounding days
25% lower than surrounding days
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 |
|---|---|---|---|---|
| Bakersfield, CA | 158.6 µg/m³ | 13.1 | Aug 22, 2020 | Worst day on record |
| Fresno, CA | 153.5 µg/m³ | 18.8 | Aug 22, 2020 | #6 of its top days |
| Sacramento--Roseville--Arden-Arcade, CA | 117 µg/m³ | 23.8 | Aug 22, 2020 | #11 of its top days |
| Stockton-Lodi, CA | 102 µg/m³ | 16.8 | Aug 20, 2020 | #11 of its top days |
| San Francisco-Oakland-Hayward, CA | 99.9 µg/m³ | 8.0 | Aug 23, 2020 | #15 of its top days |
| San Jose-Sunnyvale-Santa Clara, CA | 85.3 µg/m³ | 3.9 | Aug 19, 2020 | #10 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.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 215 PM2.5 samples in the candidate CBSA on 2020-08-23, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 1 PM2.5 sample in the candidate CBSA on 2020-08-22, identifying wildfire smoke as affecting the sample. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 24 PM2.5 samples in the candidate CBSA on 2020-08-23, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 24 PM2.5 samples in the candidate CBSA on 2020-08-24, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier RT — Wildfire-U. S.
EPA AQS carries an agency-submitted request-exclusion qualifier (RT, Wildfire-U. S.) on 24 PM2.5 samples in the candidate CBSA on 2020-08-23, 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 IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 208 PM2.5 samples in the candidate CBSA on 2020-08-24, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 217 PM2.5 samples in the candidate CBSA on 2020-08-21, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 217 PM2.5 samples in the candidate CBSA on 2020-08-20, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IE — Demolition.
EPA AQS carries an agency-submitted informational qualifier (IE, Demolition.) on 1 PM2.5 sample in the candidate CBSA on 2020-08-22, identifying demolition as affecting the sample. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier RT — Wildfire-U. S.
EPA AQS carries an agency-submitted request-exclusion qualifier (RT, Wildfire-U. S.) on 70 PM2.5 samples in the candidate CBSA on 2020-08-21, 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 IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 218 PM2.5 samples in the candidate CBSA on 2020-08-22, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier RT — Wildfire-U. S.
EPA AQS carries an agency-submitted request-exclusion qualifier (RT, Wildfire-U. S.) on 72 PM2.5 samples in the candidate CBSA on 2020-08-20, 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 IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 96 PM2.5 samples in the candidate CBSA on 2020-08-22, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 72 PM2.5 samples in the candidate CBSA on 2020-08-23, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 24 PM2.5 samples in the candidate CBSA on 2020-08-20, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 24 PM2.5 samples in the candidate CBSA on 2020-08-24, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 1 PM2.5 sample in the candidate CBSA on 2020-08-19, identifying wildfire smoke as affecting the sample. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 24 PM2.5 samples in the candidate CBSA on 2020-08-21, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 190 PM2.5 samples in the candidate CBSA on 2020-08-19, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IE — Demolition.
EPA AQS carries an agency-submitted informational qualifier (IE, Demolition.) on 1 PM2.5 sample in the candidate CBSA on 2020-08-19, identifying demolition as affecting the sample. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 24 PM2.5 samples in the candidate CBSA on 2020-08-21, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 24 PM2.5 samples in the candidate CBSA on 2020-08-20, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 24 PM2.5 samples in the candidate CBSA on 2020-08-19, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 96 PM2.5 samples in the candidate CBSA on 2020-08-19, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 24 PM2.5 samples in the candidate CBSA on 2020-08-22, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier RT — Wildfire-U. S.
EPA AQS carries an agency-submitted request-exclusion qualifier (RT, Wildfire-U. S.) on 72 PM2.5 samples in the candidate CBSA on 2020-08-24, 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.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 48 PM2.5 samples in the candidate CBSA on 2020-08-22, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 120 PM2.5 samples in the candidate CBSA on 2020-08-23, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier RT — Wildfire-U. S.
EPA AQS carries an agency-submitted request-exclusion qualifier (RT, Wildfire-U. S.) on 25 PM2.5 samples in the candidate CBSA on 2020-08-21, 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 IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 120 PM2.5 samples in the candidate CBSA on 2020-08-21, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 46 PM2.5 samples in the candidate CBSA on 2020-08-21, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier RT — Wildfire-U. S.
EPA AQS carries an agency-submitted request-exclusion qualifier (RT, Wildfire-U. S.) on 25 PM2.5 samples in the candidate CBSA on 2020-08-22, 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 RT — Wildfire-U. S.
EPA AQS carries an agency-submitted request-exclusion qualifier (RT, Wildfire-U. S.) on 1 PM2.5 sample in the candidate CBSA on 2020-08-23, identifying wildfire smoke as affecting the sample. A request-exclusion qualifier is an official submitting-agency causal claim, but this endpoint does not establish EPA concurrence.
AQS PM2.5 qualifier RT — Wildfire-U. S.
EPA AQS carries an agency-submitted request-exclusion qualifier (RT, Wildfire-U. S.) on 3 PM2.5 samples in the candidate CBSA on 2020-08-22, 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 RT — Wildfire-U. S.
EPA AQS carries an agency-submitted request-exclusion qualifier (RT, Wildfire-U. S.) on 25 PM2.5 samples in the candidate CBSA on 2020-08-23, 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 IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 48 PM2.5 samples in the candidate CBSA on 2020-08-23, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 122 PM2.5 samples in the candidate CBSA on 2020-08-22, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier RT — Wildfire-U. S.
EPA AQS carries an agency-submitted request-exclusion qualifier (RT, Wildfire-U. S.) on 1 PM2.5 sample in the candidate CBSA on 2020-08-21, identifying wildfire smoke as affecting the sample. A request-exclusion qualifier is an official submitting-agency causal claim, but this endpoint does not establish EPA concurrence.
NWS Dense Smoke record, SAN FRANCISCO, CALIFORNIA (2020-08-19)
Smoke from multiple wildfires across California blanketed the Bay Area giving San Francisco the worst air quality in the world
State public-health release identifies unhealthy air in fire-stricken and surrounding California regions as wildfire-smoke exposure.
Air quality advisory for wildfire smoke extended through Tuesday
Bay Area regulator attributed the contemporaneous advisory to smoke from numerous lightning-sparked wildfires across the region.
Fresno-area smoke levels from wildfires off the chart. When will it get better?
Archived contemporaneous reporting identifies wildfire smoke, including the Creek and Lake fires, as the likely source of exceptionally high Fresno-area PM2.5.
EPA monitor flag EPA attached an exceptional-event qualifier to the affected samples. The agency flagged the measurement itself; no separate agency record describes the event.
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. 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.