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Air quality · Washington, United States

Seattle Air Quality Index (AQI) today

Modelled estimate for 04:00 local time (UTC-8), refreshed 3 Nov, 07:52 UTC+0.

102 Unhealthy for sensitive groups

Live estimate · modelled

US EPA AQI04:00 UTC-8, 3 Nov Main pollutant: PM2.5

Members of sensitive groups may experience health effects. The general public is less likely to be affected.

This page uses EPA’s NowCast, which follows the last few hours, as the US government’s AirNow does. On a 24-hour average of particles, as many apps show, it is 89.

Over the next 24 hours the model expects the AQI to range from 64 around 16:00 to 100 around 05:00 (3 Nov).

189th most polluted of 849 cities worldwide right now, 1st of 25 in United States.

What to do today

  • Long walk or run outside Shorter if you have asthma or heart disease
  • Kids playing outside OK, less for kids with asthma
  • Airing the house Open
  • Mask outdoors If you are in a sensitive group

Based on the US EPA’s health statement: “Members of sensitive groups may experience health effects. The general public is less likely to be affected.” General guidance, not medical advice.

Last 24 hours and next 48

Past hours Forecast

05:00 · 88 06:00 · 86 07:00 · 83 08:00 · 82 09:00 · 81 10:00 · 82 11:00 · 82 12:00 · 82 13:00 · 80 14:00 · 78 15:00 · 77 16:00 · 77 17:00 · 80 18:00 · 85 19:00 · 89 20:00 · 92 21:00 · 95 22:00 · 99 23:00 · 102 00:00 · 105 01:00 · 105 02:00 · 105 03:00 · 103 04:00 · 102 05:00 · 100 06:00 · 99 07:00 · 99 08:00 · 98 09:00 · 97 10:00 · 94 11:00 · 90 12:00 · 84 13:00 · 77 14:00 · 71 15:00 · 66 16:00 · 64 17:00 · 65 18:00 · 67 19:00 · 70 20:00 · 74 21:00 · 79 22:00 · 83 23:00 · 87 00:00 · 88 01:00 · 88 02:00 · 89 03:00 · 89 04:00 · 87 05:00 · 86 06:00 · 85 07:00 · 86 08:00 · 87 09:00 · 88 10:00 · 87 11:00 · 87 12:00 · 88 13:00 · 88 14:00 · 87 15:00 · 85 16:00 · 85 17:00 · 85 18:00 · 85 19:00 · 84 20:00 · 82 21:00 · 80 22:00 · 78 23:00 · 78 Now

US EPA AQI per hour, UTC-8. Particles use EPA’s NowCast (a 12-hour weighted average), ozone and CO an 8-hour average. Lighter bars are the CAMS forecast.

Show as a table
TimeAQI
Mon 05:0088
Mon 06:0086
Mon 07:0083
Mon 08:0082
Mon 09:0081
Mon 10:0082
Mon 11:0082
Mon 12:0082
Mon 13:0080
Mon 14:0078
Mon 15:0077
Mon 16:0077
Mon 17:0080
Mon 18:0085
Mon 19:0089
Mon 20:0092
Mon 21:0095
Mon 22:0099
Mon 23:00102
Tue 00:00105
Tue 01:00105
Tue 02:00105
Tue 03:00103
Tue 04:00 · Now102
Tue 05:00 · Forecast100
Tue 06:00 · Forecast99
Tue 07:00 · Forecast99
Tue 08:00 · Forecast98
Tue 09:00 · Forecast97
Tue 10:00 · Forecast94
Tue 11:00 · Forecast90
Tue 12:00 · Forecast84
Tue 13:00 · Forecast77
Tue 14:00 · Forecast71
Tue 15:00 · Forecast66
Tue 16:00 · Forecast64
Tue 17:00 · Forecast65
Tue 18:00 · Forecast67
Tue 19:00 · Forecast70
Tue 20:00 · Forecast74
Tue 21:00 · Forecast79
Tue 22:00 · Forecast83
Tue 23:00 · Forecast87
Wed 00:00 · Forecast88
Wed 01:00 · Forecast88
Wed 02:00 · Forecast89
Wed 03:00 · Forecast89
Wed 04:00 · Forecast87
Wed 05:00 · Forecast86
Wed 06:00 · Forecast85
Wed 07:00 · Forecast86
Wed 08:00 · Forecast87
Wed 09:00 · Forecast88
Wed 10:00 · Forecast87
Wed 11:00 · Forecast87
Wed 12:00 · Forecast88
Wed 13:00 · Forecast88
Wed 14:00 · Forecast87
Wed 15:00 · Forecast85
Wed 16:00 · Forecast85
Wed 17:00 · Forecast85
Wed 18:00 · Forecast85
Wed 19:00 · Forecast84
Wed 20:00 · Forecast82
Wed 21:00 · Forecast80
Wed 22:00 · Forecast78
Wed 23:00 · Forecast78

Pollutants this hour

  • PM2.5 34.5 µg/m³ 24-hour mean 29.6 µg/m³ · 2.0× WHO’s 24-hour guideline (15) 102
  • PM10 36 µg/m³ 34
  • O₃ 9 µg/m³ 2
  • NO₂ 49 µg/m³ 25
  • SO₂ 4 µg/m³ 1
  • CO 0.28 mg/m³ 3

Modelled concentrations at the city’s location (CAMS). The sub-index uses the same averaging as the headline, so the highest one is the AQI.

Nearby cities

City AQI
Vancouver Canada 108
Portland Oregon 74
Calgary Canada 54
Edmonton Canada 55
San Francisco California 55
San Jose California 59
Los Angeles California 88

Where this number comes from

The Copernicus Atmosphere Monitoring Service (CAMS) forecasts air pollution worldwide on a grid (about 11 km over Europe, about 45 km elsewhere). We take the grid value at Seattle’s coordinates and score it with the US EPA’s method. It is a model, not a measurement: a nearby monitoring station can read quite differently, especially next to busy roads or during fires and dust storms.

Full methodology · Data: CAMS via Open-Meteo (CC BY 4.0); city list: GeoNames (CC BY 4.0).

  • Good 0–50
  • Moderate 51–100
  • Unhealthy for sensitive groups 101–150
  • Unhealthy 151–200
  • Very unhealthy 201–300
  • Hazardous 301–500

Questions

What is the AQI in Seattle right now?
102 on the US EPA scale (Unhealthy for sensitive groups) at 04:00 UTC-8, 3 Nov. PM2.5 is the pollutant with the highest sub-index. This is a modelled estimate from the Copernicus Atmosphere Monitoring Service (CAMS), not a reading from a monitoring station.

Is it safe to exercise outside in Seattle today?
For most people, yes; people with asthma, heart or lung disease, older adults and children should take it easier. The EPA’s statement for “Unhealthy for sensitive groups”: Members of sensitive groups may experience health effects. The general public is less likely to be affected. General guidance, not medical advice.

Will the air in Seattle get better or worse tomorrow?
Over the next 24 hours the model expects the AQI to range from 64 around 16:00 to 100 around 05:00 (3 Nov). Forecasts beyond a day are less certain.

How does Seattle compare with other cities?
Right now it is the 189th most polluted of 849 cities we track worldwide, and 1st of 25 in United States, all on the same US EPA scale.

Why does another app show a different AQI for Seattle?
Apps differ in source (government stations, low-cost sensors or a model like this one), in scale (US EPA, European, or a national index) and in averaging (hourly or NowCast, 8-hour, 24-hour). This page uses the US EPA AQI with EPA’s NowCast for particles, computed from the CAMS forecast for the city’s location.