Napa Valley’s air quality plunged into “very unhealthy” territory for a time Wednesday, even in the south county which had escaped the worst of Glass Fire smoke.
Air quality in the city of Napa started off “healthy” Wednesday, but degenerated into the purple range by late morning, meaning the air was considered “very unhealthy” for everyone, not just the most vulnerable populations.
By early afternoon, the city’s air quality had improved marginally to just “unhealthy.”
Don’t expect any immediate dramatic improvements in air quality, said Dean Peterson, a meteorologist with the National Weather Service.
“It looks like your air quality will be pretty bad through Friday, Peterson said Wednesday afternoon, blaming smoke from the Upvalley’s Glass Fire.
Last month’s Hennessey Fire burned far more acreage in Napa and surrounding counties than the Glass Fire, but it burned much hotter, sending its smoke higher in the air, Peterson said.
The Hennessey Fire created a high canopy of smoke over Napa, but the air at ground level didn’t approach today’s Air Quality Index high readings from the Glass Fire, he said.
The Bay Area Air Quality Management District said Napa’s air scored a 204 AQI reading at noon or “very unhealthy,” increasing the health threat for everyone.
Under AQI guidelines, when air is above 200, active children and adults and people with respiratory disease, such asthma, should avoid all outdoor exertion, and everyone else, especially children should limit outdoor exertion.
By 1 p.m., the AQI reading had dropped to 191.
Most of the Bay Area scored below 100 AQI at midday Wednesday, falling in the good and moderate categories, except for Vallejo with a reading of 172.
Peterson said the Glass Fire on Wednesday was “more like a campfire than an inferno,” its smoke trapped beneath higher levels of air and staying in the Napa Valley.
“All that smoke has to go somewhere,” and in the case of the Glass Fire, on a day with few breezes, that somewhere is to stay right here, Peterson said.
It’s possible that the Red Flag warning that the National Weather Service is calling for Thursday and Friday will shake up the air mass over the valley and bring improved air, although it increases the danger of more fires, Peterson said.
Until then, “there will be periods when it’s better and periods when it’s worse,” Peterson said. The communities of the Napa Valley are just so close to the Glass Fire that there’s little escaping the smoke, he said.
During the Hennessey Fire in August, Napa had days when the sky was orange and the sun red, but the AQI was generally below 150.
Watch Now: Aerial video reveals scorched landscape from Glass Fire
You can reach City Editor Kevin Courtney at firstname.lastname@example.org or at 707-256-2217.
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