The Sacramento region on Friday is expected to experience its worst air quality day since smoke from the Camp Fire passed through, according to local air districts.
With a particulate matter (PM2.5) Air Quality Index forecast of 102, Friday has been categorized as “unhealthy for sensitive groups,” according to SparetheAir.com.
The Sacramento Metropolitan Air Quality Management District made Thursday a no-burn day after discouraging burning Wednesday.
Friday will mark the worst AQI reading since Nov. 21 (145), which was the last of 13 consecutive unhealthy air days brought on by wildfire smoke. That stretch included the second-worst air day in Sacramento history as recorded by modern standards, with an AQI of 314.
Light southeasterly winds will carried pollutant matter into the Sacramento Valley, according to Spare the Air’s forecast. Spare the Air is maintained by the Sacramento Metropolitan, El Dorado, Feather River, Placer and Yolo-Solano air quality districts.
Poor air quality, with AQI readings exceeding 100, are common this time of year. The region saw three such days in each of the past two Januaries, and seven of them in January 2015.
Though some people may associate poor air quality with smoky conditions or the summertime, and so-called “Spare the Air days” are only put into place from May to October, the start of winter brings conditions conducive to air pollutants in Northern California.
A 1999 research paper written by California Air Resources Board Nehzat Motallebi said PM2.5 pollution during Sacramento winters is created by weather factors – low inversion layers, low winds and cool temperatures – and residential wood burning.
A 2017 report by the Cleaner Air Partnership said Sacramento County has reduced PM2.5 levels by 60 percent since 1998.