Sacramento air quality reaches ‘very unhealthy’ level, but conditions could change Sunday

Sacramento once again reached very unhealthy levels for air quality, with a measurement of 200 by Spare the Air on Saturday afternoon — but conditions could change soon and the air may start to clear this weekend.

The Sacramento Metropolitan Air Quality Management District issued an air alert Saturday, advising residents to avoid prolonged or heavy exertion outdoors. According to the alert, Davis is seeing even higher levels of smoke pollution, reaching a very unhealthy AQI of 204.

The primary pollutant currently darkening the California sky is PM2.5, which is considered typical of wildfire smoke, officials said. Earlier in the week, the National Weather Service in the Bay Area reported that large chunks of ash, with a size greater than PM10, exceeded the measuring capacity of its sensors, making it difficult to accurately assess air quality dangers.

Those with respiratory issues or heart disease, children and elderly people are the groups facing the most risk and should avoid all physical activity outdoors, the district said. However, the general population may also experience respiratory effects.

“Persons with cardiopulmonary disease and the elderly may experience significant aggravation of heart or lung disease and premature mortality,” the district wrote in an alert.

The Interagency Wildland Fire Air Quality Response Program said the August Complex, which became the largest wildfire in California history, and many other wildfires across Northern and Central California continue to bring smoke into the region. With plentiful dry fuels, smoke and extreme fire conditions are continuing.

The agency also said earlier this week that smoke that hanging in upper levels of the atmosphere was descending to the ground level, where air quality monitors are located, which helped to explain the worsening air quality in the region.

There was some hope for air quality conditions to improve later this weekend, but with an increased risk in fire danger. A slight change predicted in the winds could present elevated risks as the large wildfires continue to burn in Northern California.

Scott Rowe, a meteorologist with the weather service in Sacramento, said Friday an onshore flow moving west to east was expected to return to California on Sunday afternoon and continue through Thursday. He said the onshore flow can produce wind strong enough to push some of the wildfire smoke out of the region.

The Sacramento Air Quality Management District predicted some relief to come Sunday, with AQI levels in the region potentially dropping down to 187, though the levels of PM2.5 in the air will likely remain unhealthy.

The wind will likely be stronger than what the region was experiencing Friday, so that could elevate fire danger as firefighters continue to work to contain the wildfires, Rowe said.

The onshore flow, however, will also increase relative humidity levels, Rowe said. Increased humidity levels help firefighters gain an advantage against wildfires.

An improvement to air quality in the Sacramento region also will depend on how much smoke the wildfires continue to produce and how much containment firefighters can gain, Rowe said.

This story was originally published September 11, 2020 at 10:39 AM.