SmogRank / United States / Oregon

Air quality in Ontario

Oregon, United States. Over the last 7 days its air rated Good, the 2,101st most polluted of 2,680 cities measured.

Latest hour36US AQI
Good

PM2.5 6.5 µg/m³, 0.4× the WHO 24-hour guideline, at local time. Too few hours in the last 24 for a 24-hour average.

Last 7 days: about usual for early October (4.6 µg/m³).

Where Ontario ranks

24 hours–not enough data
7 days#2,101of 2,680, at 29 US AQI (5.2 µg/m³)
30 days#2,439of 2,888, at 26 US AQI (4.6 µg/m³)
This year#753of 2,734, at 56 US AQI (11.6 µg/m³)

Why it ranks here

Seasonal. Over the past year its worst months were July, averaging up to 31.9 µg/m³ against 4.3 in its cleanest month. Seasonal peaks usually come from heating, crop burning, fire or dust seasons.

Based on Ontario's own measurements; causes are the usual kinds for a pattern like this, not a confirmed source.

Bad-air episodes that reached Ontario

Times when Ontario and many cities around it had PM2.5 at twice their usual or more on the same days. All episodes.

The last 12 months, day by day

1102031Nov 2025DecJan 2026FebMarAprMayJunJulAugSepOct2025-11-01: 21.2 µg/m³2025-11-02: 6.1 µg/m³2025-11-03: 6.2 µg/m³2025-11-04: 7.2 µg/m³2025-11-05: 5.6 µg/m³2025-11-06: 4.0 µg/m³2025-11-07: 4.5 µg/m³2025-11-08: 9.0 µg/m³2025-11-09: 12.0 µg/m³2025-11-10: 13.5 µg/m³2025-11-11: 18.5 µg/m³2025-11-12: 21.1 µg/m³2025-11-13: 17.3 µg/m³2025-11-14: no daily value, only 12 of the 18 hours a day needs2025-11-15: no daily value, only 8 of the 18 hours a day needs2025-11-16: no daily value, only 10 of the 18 hours a day needs2025-11-17: no daily value, only 12 of the 18 hours a day needs2025-11-18: no daily value, only 14 of the 18 hours a day needs2025-11-19: no daily value, only 8 of the 18 hours a day needs2025-11-20: 13.8 µg/m³2025-11-21: 13.7 µg/m³2025-11-22: 16.9 µg/m³2025-11-23: 17.8 µg/m³2025-11-24: 13.8 µg/m³2025-11-25: 11.6 µg/m³2025-11-26: 7.1 µg/m³2025-11-27: 11.5 µg/m³2025-11-28: 9.8 µg/m³2025-11-29: 6.4 µg/m³2025-11-30: 6.1 µg/m³2025-12-01: 13.9 µg/m³2025-12-02: 7.1 µg/m³2025-12-03: 6.4 µg/m³2025-12-04: 12.6 µg/m³2025-12-05: 10.0 µg/m³2025-12-06: no daily value, only 7 of the 18 hours a day needs2025-12-07: no daily value, only 13 of the 18 hours a day needs2025-12-08: 10.5 µg/m³2025-12-09: 9.4 µg/m³2025-12-10: 11.6 µg/m³2025-12-11: 9.3 µg/m³2025-12-12: 13.3 µg/m³2025-12-13: 20.9 µg/m³2025-12-14: 24.3 µg/m³2025-12-15: 23.2 µg/m³2025-12-16: 20.5 µg/m³2025-12-17: 8.8 µg/m³2025-12-18: 5.4 µg/m³2025-12-19: 8.6 µg/m³2025-12-20: 8.9 µg/m³2025-12-21: 5.4 µg/m³2025-12-22: 7.1 µg/m³2025-12-23: 7.9 µg/m³2025-12-24: 6.7 µg/m³2025-12-25: 4.6 µg/m³2025-12-26: 4.1 µg/m³2025-12-27: no daily value, only 8 of the 18 hours a day needs2025-12-28: 8.8 µg/m³2025-12-29: 9.2 µg/m³2025-12-30: 13.3 µg/m³2025-12-31: 22.6 µg/m³2026-01-01: 22.0 µg/m³2026-01-02: 15.2 µg/m³2026-01-03: 8.6 µg/m³2026-01-04: 5.0 µg/m³2026-01-05: 7.1 µg/m³2026-01-06: 7.2 µg/m³2026-01-07: 4.1 µg/m³2026-01-08: 3.8 µg/m³2026-01-09: 8.3 µg/m³2026-01-10: 14.6 µg/m³2026-01-11: 16.6 µg/m³2026-01-12: 20.5 µg/m³2026-01-13: 26.9 µg/m³2026-01-14: 33.9 µg/m³2026-01-15: 25.9 µg/m³2026-01-16: 16.0 µg/m³2026-01-17: 15.3 µg/m³2026-01-18: 11.4 µg/m³2026-01-19: 11.0 µg/m³2026-01-20: 10.0 µg/m³2026-01-21: 15.1 µg/m³2026-01-22: 16.6 µg/m³2026-01-23: 10.7 µg/m³2026-01-24: 13.5 µg/m³2026-01-25: 20.4 µg/m³2026-01-26: 24.4 µg/m³2026-01-27: 23.9 µg/m³2026-01-28: 15.0 µg/m³2026-01-29: 22.9 µg/m³2026-01-30: 26.2 µg/m³2026-01-31: 26.0 µg/m³2026-02-01: 26.2 µg/m³2026-02-02: 27.3 µg/m³2026-02-03: 19.9 µg/m³2026-02-04: 25.6 µg/m³2026-02-05: 22.4 µg/m³2026-02-06: 21.0 µg/m³2026-02-07: 24.3 µg/m³2026-02-08: 15.5 µg/m³2026-02-09: 5.3 µg/m³2026-02-10: 7.2 µg/m³2026-02-11: 6.6 µg/m³2026-02-12: 10.0 µg/m³2026-02-13: 10.6 µg/m³2026-02-14: 9.2 µg/m³2026-02-15: 9.0 µg/m³2026-02-16: 10.8 µg/m³2026-02-17: 3.7 µg/m³2026-02-18: no daily value, readings left out by our checks (a stuck monitor, error codes, or a reading its neighbours contradict)2026-02-19: 4.8 µg/m³2026-02-20: 5.5 µg/m³2026-02-21: 4.5 µg/m³2026-02-22: 3.8 µg/m³2026-02-23: 5.6 µg/m³2026-02-24: 5.8 µg/m³2026-02-25: 6.2 µg/m³2026-02-26: 6.0 µg/m³2026-02-27: 6.8 µg/m³2026-02-28: 10.7 µg/m³2026-03-01: 13.4 µg/m³2026-03-02: 14.6 µg/m³2026-03-03: 6.7 µg/m³2026-03-04: 4.7 µg/m³2026-03-05: no daily value, only 11 of the 18 hours a day needs2026-03-06: 3.7 µg/m³2026-03-07: 4.8 µg/m³2026-03-08: 6.2 µg/m³2026-03-09: 5.2 µg/m³2026-03-10: 3.8 µg/m³2026-03-11: 4.7 µg/m³2026-03-12: 5.1 µg/m³2026-03-13: 4.6 µg/m³2026-03-14: 4.0 µg/m³2026-03-15: 4.4 µg/m³2026-03-16: 5.8 µg/m³2026-03-17: 6.9 µg/m³2026-03-18: 8.2 µg/m³2026-03-19: 8.8 µg/m³2026-03-20: 10.2 µg/m³2026-03-21: 5.3 µg/m³2026-03-22: 4.7 µg/m³2026-03-23: 5.8 µg/m³2026-03-24: 6.1 µg/m³2026-03-25: 6.1 µg/m³2026-03-26: 3.6 µg/m³2026-03-27: 5.4 µg/m³2026-03-28: 9.3 µg/m³2026-03-29: 6.3 µg/m³2026-03-30: 3.6 µg/m³2026-03-31: 4.6 µg/m³2026-04-01: 6.3 µg/m³2026-04-02: 3.5 µg/m³2026-04-03: 4.4 µg/m³2026-04-04: 6.5 µg/m³2026-04-05: 5.6 µg/m³2026-04-06: 5.6 µg/m³2026-04-07: 4.8 µg/m³2026-04-08: 4.1 µg/m³2026-04-09: 5.9 µg/m³2026-04-10: 4.1 µg/m³2026-04-11: 3.8 µg/m³2026-04-12: 3.7 µg/m³2026-04-13: no daily value, only 15 of the 18 hours a day needs2026-04-14: 3.6 µg/m³2026-04-15: 3.7 µg/m³2026-04-16: 3.4 µg/m³2026-04-17: 4.7 µg/m³2026-04-18: 4.1 µg/m³2026-04-19: 4.1 µg/m³2026-04-20: 4.7 µg/m³2026-04-21: 4.4 µg/m³2026-04-22: 3.4 µg/m³2026-04-23: no daily value, only 3 of the 18 hours a day needs2026-04-24: 3.5 µg/m³2026-04-25: 3.9 µg/m³2026-04-26: 4.1 µg/m³2026-04-27: 3.9 µg/m³2026-04-28: 4.6 µg/m³2026-04-29: 4.6 µg/m³2026-04-30: 4.7 µg/m³2026-05-01: 5.4 µg/m³2026-05-02: 6.7 µg/m³2026-05-03: 5.3 µg/m³2026-05-04: 4.6 µg/m³2026-05-05: 4.5 µg/m³2026-05-06: 4.4 µg/m³2026-05-07: 4.3 µg/m³2026-05-08: 4.2 µg/m³2026-05-09: 4.1 µg/m³2026-05-10: 4.9 µg/m³2026-05-11: 3.8 µg/m³2026-05-12: 5.5 µg/m³2026-05-13: 4.6 µg/m³2026-05-14: 3.6 µg/m³2026-05-15: 3.9 µg/m³2026-05-16: 3.6 µg/m³2026-05-17: 3.4 µg/m³2026-05-18: 3.5 µg/m³2026-05-19: 3.8 µg/m³2026-05-20: 4.3 µg/m³2026-05-21: 3.6 µg/m³2026-05-22: 3.8 µg/m³2026-05-23: 4.9 µg/m³2026-05-24: 4.0 µg/m³2026-05-25: 4.7 µg/m³2026-05-26: 3.8 µg/m³2026-05-27: 4.0 µg/m³2026-05-28: 4.6 µg/m³2026-05-29: 3.9 µg/m³2026-05-30: 3.6 µg/m³2026-05-31: 3.7 µg/m³2026-06-01: 3.9 µg/m³2026-06-02: 4.5 µg/m³2026-06-03: 5.6 µg/m³2026-06-04: 3.8 µg/m³2026-06-05: 4.0 µg/m³2026-06-06: 5.5 µg/m³2026-06-07: 5.6 µg/m³2026-06-08: 3.9 µg/m³2026-06-09: 3.9 µg/m³2026-06-10: no daily value, readings left out by our checks (a stuck monitor, error codes, or a reading its neighbours contradict)2026-06-11: 3.5 µg/m³2026-06-12: 4.1 µg/m³2026-06-13: 3.5 µg/m³2026-06-14: 3.6 µg/m³2026-06-15: 4.5 µg/m³2026-06-16: 4.6 µg/m³2026-06-17: 3.6 µg/m³2026-06-18: 3.9 µg/m³2026-06-19: 5.0 µg/m³2026-06-20: 5.1 µg/m³2026-06-21: 5.4 µg/m³2026-06-22: 4.2 µg/m³2026-06-23: 4.4 µg/m³2026-06-24: 4.7 µg/m³2026-06-25: 4.2 µg/m³2026-06-26: 4.3 µg/m³2026-06-27: 3.5 µg/m³2026-06-28: 3.4 µg/m³2026-06-29: 3.7 µg/m³2026-06-30: 4.0 µg/m³2026-07-01: 3.6 µg/m³2026-07-02: 3.8 µg/m³2026-07-03: 3.7 µg/m³2026-07-04: 6.8 µg/m³2026-07-05: 5.4 µg/m³2026-07-06: 8.8 µg/m³2026-07-07: 8.3 µg/m³2026-07-08: 6.2 µg/m³2026-07-09: 4.7 µg/m³2026-07-10: 6.2 µg/m³2026-07-11: 4.9 µg/m³2026-07-12: 8.3 µg/m³2026-07-13: 8.4 µg/m³2026-07-14: 5.0 µg/m³2026-07-15: 7.0 µg/m³2026-07-16: 6.8 µg/m³2026-07-17: 17.4 µg/m³2026-07-18: 34.1 µg/m³2026-07-19: 41.3 µg/m³2026-07-20: 58.6 µg/m³2026-07-21: 53.5 µg/m³2026-07-22: 43.7 µg/m³2026-07-23: 29.2 µg/m³2026-07-24: 38.4 µg/m³2026-07-25: 20.9 µg/m³2026-07-26: 124.0 µg/m³2026-07-27: 135.0 µg/m³2026-07-28: 113.0 µg/m³2026-07-29: 74.8 µg/m³2026-07-30: 53.1 µg/m³2026-07-31: 55.4 µg/m³2026-08-01: 28.2 µg/m³2026-08-02: 16.0 µg/m³2026-08-03: 50.0 µg/m³2026-08-04: 59.4 µg/m³2026-08-05: 35.2 µg/m³2026-08-06: 40.9 µg/m³2026-08-07: 70.3 µg/m³2026-08-08: 51.8 µg/m³2026-08-09: 28.1 µg/m³2026-08-10: 28.9 µg/m³2026-08-11: 24.1 µg/m³2026-08-12: 19.9 µg/m³2026-08-13: no daily value, only 9 of the 18 hours a day needs2026-08-14: no daily value, only 15 of the 18 hours a day needs2026-08-15: 6.6 µg/m³2026-08-16: 3.7 µg/m³2026-08-17: 7.6 µg/m³2026-08-18: 10.4 µg/m³2026-08-19: 9.3 µg/m³2026-08-20: 10.1 µg/m³2026-08-21: 10.3 µg/m³2026-08-22: 7.3 µg/m³2026-08-23: 8.1 µg/m³2026-08-24: 6.6 µg/m³2026-08-25: 7.5 µg/m³2026-08-26: 6.6 µg/m³2026-08-27: 7.3 µg/m³2026-08-28: 8.6 µg/m³2026-08-29: 5.4 µg/m³2026-08-30: 4.3 µg/m³2026-08-31: 6.1 µg/m³2026-09-01: 6.3 µg/m³2026-09-02: no daily value, only 13 of the 18 hours a day needs2026-09-03: 3.4 µg/m³2026-09-04: 3.9 µg/m³2026-09-05: 4.8 µg/m³2026-09-06: 4.2 µg/m³2026-09-07: 3.8 µg/m³2026-09-08: 4.9 µg/m³2026-09-09: 4.3 µg/m³2026-09-10: 4.4 µg/m³2026-09-11: 4.2 µg/m³2026-09-12: 5.3 µg/m³2026-09-13: 3.6 µg/m³2026-09-14: 4.0 µg/m³2026-09-15: 5.4 µg/m³2026-09-16: 4.5 µg/m³2026-09-17: 5.3 µg/m³2026-09-18: 3.9 µg/m³2026-09-19: 4.4 µg/m³2026-09-20: 4.5 µg/m³2026-09-21: 4.4 µg/m³2026-09-22: 5.4 µg/m³2026-09-23: 3.9 µg/m³2026-09-24: 4.7 µg/m³2026-09-25: 4.2 µg/m³2026-09-26: 3.6 µg/m³2026-09-27: 3.5 µg/m³2026-09-28: 3.9 µg/m³2026-09-29: 4.9 µg/m³2026-09-30: 4.2 µg/m³2026-10-01: 4.4 µg/m³2026-10-02: 7.3 µg/m³2026-10-03: 8.1 µg/m³
64 of 348 measured days were over the WHO 24-hour guideline (15 µg/m³). 17 days without a value: 15 with readings for part of the day (a day needs 18 hours), 2 with readings left out by our checks; point at a grey square for its reason (why days go blank). One row per month, one square per local day.
Good0–50
Moderate51–100
Sensitive groups101–150
Unhealthy151–200
Very unhealthy201–300
Hazardous301+

The US EPA's Air Quality Index for PM2.5 (2024 breakpoints). Show values as: µg/m³ · US AQI · India AQI · China AQI · European AQI · UK DAQI · Canada AQHI+. About the scales

Last 4 days, hour by hour

15304 Oct 17:00 local, 2026-10-04 23:00 UTC: 5.6 µg/m³4 Oct 18:00 local, 2026-10-05 00:00 UTC: 5.3 µg/m³4 Oct 19:00 local, 2026-10-05 01:00 UTC: 5.6 µg/m³4 Oct 20:00 local, 2026-10-05 02:00 UTC: 6.5 µg/m³Oct 1Oct 2Oct 3Oct 4
Ontario's local time; hover a bar for UTC. Dashed line: WHO 24-hour guideline (15 µg/m³).

Where it stood each day

Top 10Top 100#1#10#100#1,000#3,193NovDecJanFebMarAprMayJunJulAugSep#820
Its rank on each day's world board, #1 being the most polluted city that day. Higher is worse. Each gridline down is ten times the rank above it (#1, #10, #100, #1,000), so the top places get the most room. See it among every city.

2026 against 2025, month by month

15Jan 2025: 12.9 µg/m³Jan 2026: 16.1 µg/m³JanFeb 2025: 9.2 µg/m³Feb 2026: 11.6 µg/m³FebMar 2025: 5.1 µg/m³Mar 2026: 6.2 µg/m³MarApr 2025: 5.1 µg/m³Apr 2026: 4.4 µg/m³AprMay 2025: 4.4 µg/m³May 2026: 4.3 µg/m³MayJun 2025: 4.4 µg/m³Jun 2026: 4.3 µg/m³JunJul 2025: 5.0 µg/m³Jul 2026: 31.9 µg/m³JulAug 2025: 7.0 µg/m³Aug 2026: 20.0 µg/m³AugSep 2025: 9.3 µg/m³Sep 2026: 4.4 µg/m³SepOct 2025: 6.3 µg/m³OctNov 2025: 11.4 µg/m³NovDec 2025: 11.2 µg/m³Dec
Faded bars: 2025. A month shows once it has 10 measured days.

This week against past years

This weekThis week: 5.2 µg/m³5.220252025: 6.6 µg/m³6.620242024: 3.7 µg/m³3.720232023: 2.8 µg/m³2.8
Mean PM2.5 for 27 Sept to 3 Oct in each year. Dashed line: WHO 24-hour guideline.

Monitors

PM2.5 from 1 reference monitor, updated hourly.

StationOperatorType
Ontario May RobertsUS Public DomainAirNowReference

The city's value is the median of its reference monitors each hour, when at least a third of them report (three are always enough); low-cost sensors are listed but not counted when reference monitors exist. Data via OpenAQ; licences as listed. How we rank. Embed this on your site.

Use this page

SmogRank, PM2.5 daily means, Ontario, United States, 4 Oct 2025 – 3 Oct 2026, smogrank.com/us/ontario-oregon (accessed 5 Oct 2026).

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You're welcome to reuse a single chart, image or figure with this citation and a link. Terms. Raw monitor readings in bulk are published by OpenAQ, under each provider's licence.

Other cities in United States

30-day averages, US AQI. All of United States.

Updated 2026-10-05 03:07 UTC. Values are PM2.5 (fine particles), the median of each city's monitors, as the US AQI PM2.5 sub-index.