Processed on 2024-03-04 14:13:58 PST.


Disclaimer: Data presented here come from a variety of sources and do not represent official EPA measurements. Please visit AirNow for official measurements.


Cumulative exposure to smoke is an important public health metric. This report summarizes the cumulative number of days air quality monitors in Washington spent in each AQI category during the the month of May.

The tables below include only permanent monitors measuring PM2.5 and show cumulative exposure under existing NAAQS (National Ambient Air Quality Standards) and under the 2024 revised standards for PM2.5.

In the tables and plots below, ‘Old’ designates cumulative days calculated using the 2023 PM2.5 NAAQS while ‘New’ is calculated using the 2024 revised PM2.5 NAAQS. The impact of the NAAQS revision is quite clear.

May in Washington

May 2014 – 30 permanent monitors

Good Moderate USG Unhealthy Very Unhealthy Hazardous Missing
Old 876 0 0 0 0 0 52
New 864 12 0 0 0 0 52

May 2015 – 41 permanent monitors

Good Moderate USG Unhealthy Very Unhealthy Hazardous Missing
Old 885 3 0 0 0 0 72
New 869 19 0 0 0 0 72

May 2016 – 112 permanent monitors

Good Moderate USG Unhealthy Very Unhealthy Hazardous Missing
Old 1158 2 0 0 0 0 56
New 1122 38 0 0 0 0 56

May 2017 – 52 permanent monitors

Good Moderate USG Unhealthy Very Unhealthy Hazardous Missing
Old 1318 3 0 0 0 0 87
New 1298 23 0 0 0 0 87

May 2018 – 130 permanent monitors

Good Moderate USG Unhealthy Very Unhealthy Hazardous Missing
Old 1429 6 1 0 0 0 100
New 1389 46 1 0 0 0 100

May 2019 – 67 permanent monitors

Good Moderate USG Unhealthy Very Unhealthy Hazardous Missing
Old 1648 22 0 0 0 0 154
New 1559 111 0 0 0 0 154

May 2020 – 129 permanent monitors

Good Moderate USG Unhealthy Very Unhealthy Hazardous Missing
Old 1717 0 0 0 0 0 139
New 1702 15 0 0 0 0 139

May 2021 – 71 permanent monitors

Good Moderate USG Unhealthy Very Unhealthy Hazardous Missing
Old 1940 5 0 0 0 0 103
New 1915 30 0 0 0 0 103

May 2022 – 83 permanent monitors

Good Moderate USG Unhealthy Very Unhealthy Hazardous Missing
Old 1882 3 0 0 0 0 195
New 1877 8 0 0 0 0 195

May 2023 – 106 permanent monitors

Good Moderate USG Unhealthy Very Unhealthy Hazardous Missing
Old 2101 88 1 0 0 0 178
New 2016 173 1 0 0 0 178