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2010-2020 Wildfire Seasons: A 10-year Comparison

October 16, 2020

Although a month has passed, the days of very unhealthy to hazardous smoke levels here and across Washington state won’t soon be forgotten.

On September 8, 2020, a massive smoke plume from California and Oregon wildfires, began traveling across Washington, creating very poor air quality in its path. Below is a satellite image of the smoke cloud.



Fortunately, a warning from the Washington State Department of Ecology’s air quality forecasters that the smoke was heading across the state, gave local agencies an opportunity to get the word out. State forecasters predicted that this "massive" cloud of smoke would likely result in very unhealthy to hazardous air quality in Spokane. The National Weather Service in Spokane issued an air quality alert on Thursday evening and the news media helped get the word out to help residents be aware and prepare. 

Just as predicted, late Friday night, September 11, the smoke reached eastern Washington. Spokane’s air quality quickly degraded and Saturday morning was in the very unhealthy range in a matter of hours. This was the beginning of  seven consecutive days of air quality in the unhealthy to hazardous range on the Air Quality Index. Spokane has had wildfire seasons with more days in unhealthy ranges, but none with these high of concentrations of smoke. 

September 2020 was our first, 24-hour period that averaged in the hazardous range for smoke particles, and it happened on four consecutive days. We’ve experienced high particle pollution from dust storms and certainly Mt. St. Helen’s ash. But as far as wildfire smoke, levels measured from September 12-18 were unprecedented in the more than 50 years Spokane Clean Air has been measuring air pollution.  

The national, health-based standard for fine particles (PM2.5) was established in 1998. Prior to 1998, small and large particles were not separated when measured, therefore that data is difficult to compare as it contains large (dust) and small (smoke) particles combined. 

In June 2021, Spokane Clean Air and our local partners will again be promoting "Smoke Ready Week" with the goal of encouraging people to be prepared before the wildfire smoke arrives. Meanwhile, information and resources are available here for those who would like to start planning now.

Here’s how September’s wildfire smoke compares with the past 10 wildfire seasons. 

Wildfire Season Number of days air quality did not meet health-based standards due to
wildfire smoke
Highest daily AQ value  AQI Category Number of days in this category
2020 7 479 Hazardous 4
2019 2 129 Unhealthy for Some 2
2018 13 257 Very Unhealthy 1

16 (10 in Aug)
(6 in Sep) 

256 Very Unhealthy 3
2016 0 n/a    
2015 13 171 Unhealthy 5
2014 1 105 Unhealthy for Some 1
2013 0 n/a    
2012 2 113 Unhealthy for Some 2
2011 0 n/a    
2010 0 n/a    





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