Marine layer finally is making it safer for most residents to breathe

‘The smoke is clearing’ and air readings improving

The weather teased a large swath of the Bay Area population with a couple of forgotten-yet-familiar elements Wednesday.

The air was cool. It was breathable. And mixed in with it was a blue sky.

“For the most part,” National Weather Service meteorologist David King said, “the smoke is clearing.”

Bay Area residents have been waiting for those words ever since a flurry of lightning strikes earlier this month caused more than 300 wildfires throughout the state, creating a haze of dirty, smoky air that stayed over the region. Dozens of wildfires continue to burn in the Bay Area, including the CZU, LNU and SCU Lightning Complex wildfires.

A sizzling heat wave preceded the lightning.

“It’s finally beginning to feel a bit normal,” King said.

A Spare the Air alert issued by the Bay Area Air Quality Management District continued to be in effect through Friday.

But a marine layer of moisture and a breeze blowing from the southwest toward the northeast were the two developments that have helped to clear out much of the dirty air, King said. Hazy skies did remain throughout the area, along with areas of low clouds and low visibility just after sunrise, but King said it would not be nearly as thick or as blanketing.

“It’s the same (weather) pattern that we’ve had the last couple of days,” he said. “Nothing has really changed, except the flow is a bit stronger.”

Air management official readings at noon showed the fine particulate matter in Gilroy to be 157 and Sebastopol 151, the only unhealthful places it measured. Anything between 150-200 is considered unhealthful for anyone to breathe. Forty-eight hours earlier, some places measured more than 200, considered very unhealthful.

San Jose dipped from 102 and unhealthful for those with breathing problems at 11 a.m. to 98 at noon. Anything from 50-100 is considered moderately unhealthful air. Napa, which closed in on 200 on Monday, was at 91 at noon. Vallejo (68), Livermore (66), Pleasanton (64), Redwood City (63), Concord (61), East Oakland (56) and Berkeley (52) all had moderately healthful air.

Sebastopol showed a reading of 124; anything between 100-150 is considered unhealthful for those with breathing and other underlying issues. San Jose (97), Redwood City (73), Pleasanton (67), Livermore (56), Laney College in Oakland (54), East Oakland (53) and West Oakland (51) all had air considered moderately healthful.

Any air reading below 50 is considered healthful air. West Oakland, San Francisco, San Rafael and San Pablo all fell into that category by noon.

Smoky skies did remain in the area of the CZU Lightning Complex fire in Santa Cruz and San Mateo counties, and Purple Air, a company that measures air quality globally through sensors, had an unofficial reading of 510 in the area of Felton around 9 a.m. By 3 p.m. that reading was 264.

Fire crews and weather experts have said the effort to put out those fires has become considerably easier below 1,500 feet because of the marine layer. Humidity readings below that elevation were well above 90%, according to the weather service.

“The humidity is way up inland,” King said. “We still have ridges and hilltops above that 1,500-foot layer that are still really dry, but it’s a vast improvement. We’re really happy about it.”

Temperatures were expected to be about the same Wednesday as they were the previous 24 hours, though they might have ticked up 2-3 degrees in the far inland areas, King said. Official readings in Livermore showed high temperatures in Antioch at 94 degrees Tuesday, the region’s high mark.