Delta breeze clears smoke out of Northern California air, but pollution will return
The air remains unhealthy in the Sacramento area as wildfires continue to burn across Northern California, and some of the morning relief that helped out last week was absent at the start of this week.
But early Wednesday, the Delta breeze helped ward off smoke pollution and some of the heat. The U.S. Environmental Protection Agency’s AirNow map showed all of the capital region either in the “good” air quality index range of 0 to 50, or “moderate” range of AQI 51 to 100, as of 7 a.m.
Around 7:30 a.m., Sacramento’s skies were relatively clear and the temperature was just 59 degrees, according to the National Weather Service, as the breeze rolled in overnight.
On Monday, monitors from local air quality districts showed AQI readings in the “unhealthy” classification, from 151 to 200, across most of the capital region, according to SpareTheAir.com. Conditions were slightly better Tuesday, with AQI levels from 100 to 150 around Sacramento by 8 a.m.
Spare The Air still forecasts Sacramento and Placer to re-enter the unhealthy range later Wednesday, while conditions will be better in El Dorado, Yolo and Solano counties, where AQI levels between 100 and 130 are expected.
Particulate matter (PM2.5) pollutant levels are expected to remain above 100 through at least Friday, with AQI readings between 151 and 160 in the forecast for most of the region Wednesday according to Spare The Air, which is managed by several local air quality districts. The exception is El Dorado County, east of the capital, where a comparatively low AQI of 115 is predicted.
A couple of days last week, an overnight Delta breeze helped clear some smoke away from Sacramento and kept AQI readings significantly lower until pollutants rolled in around midday. The weather hasn’t been quite as cooperative this week, but that could change soon.
The Spare The Air forecast page says temperature “inversions” are continuing to develop each evening, “trapping smoke in the lower levels of the atmosphere.” This, combined with onshore winds and warm temperatures, are continuing to increase wildfire pollutant buildup for Sacramento.
Smoke has sullied the skies in Northern California for two weeks, ever since dozens of large fires and hundreds of smaller ones sparked during a powerful thunderstorm that brought down thousands of lightning strikes.
For much of that stretch, Sacramento’s air pollution has come primarily from the LNU Lightning Complex, which as of Tuesday morning had scorched more than 375,000 acres in parts of Napa, Sonoma, Solano, Yolo and Lake counties west of the capital. That fire continues to output smoke as it is 69% contained, Cal Fire says.
But now the poor conditions are coming from the August Complex, a 261,000-acre blaze that’s been burning in the Mendocino National Forest since Aug. 17, according to a special smoke statement issued Sunday by the U.S. Environmental Protection Agency for the mid Central Valley, which has been extended twice to include Tuesday and Wednesday.
NWS radar forecasts for near-surface smoke have shown a heavy pocket of smoke in the forest, near the convergence of Mendocino, Lake, Tehama and Glenn counties, with winds blowing it in a southeast direction. Some of it is making it to Sacramento, roughly 100 miles away.
The NWS forecasts hazy skies through at least Tuesday night, possibly clearing up by Wednesday if wildfire activity subsides.
At an AQI in the unhealthy range of 151 to 200, residents are advised to stay indoors. If you must go outside, try to limit physical activity, and if you must be active, take frequent indoor breaks. If you can smell wildfire smoke, that means you are breathing it and it is posing a threat to your health.
This story was originally published August 31, 2020 at 7:22 AM.
