Breezes Bring Cool Weather and Clear Skies : Meteorology: A low-pressure system is moving in and should arrive onshore by this evening. It has already lowered smog levels.

A cool ocean breeze began pushing into Ventura County Monday afternoon, dramatically reducing smog that had soared to unhealthful levels over the weekend.

The low-pressure system originating from Northern California began moving into the Santa Barbara and Ventura county area late Monday afternoon and is expected to arrive onshore possibly by this evening, said Kent Field, a meteorologist with the Ventura County Air Pollution Control District.

The new system is bringing cooler temperatures, replacing hot, stagnant stretches of air across Ventura County, Field said.

“We have fog and low clouds already coming into the coastline area,” he said. “As it moves in, it will knock our high-pressure system out. It’s already knocked down our pollution levels greatly.”

Field said mild Santa Ana winds, unusual for this time of year, blew a mass of polluted air stretching from Santa Barbara to Los Angeles offshore over the weekend. “Then the sea breeze kicked in and brought everything back in,” he said.

Field said the Santa Ana winds died down early Sunday and by evening high levels of smog were being reported in coastal areas such as Ventura and Oxnard as well as in the inland valleys around Thousand Oaks.

Using an air-quality standard of more than 100 as unhealthful, the county’s coastal areas registered ozone levels at 110 on the pollution standard index early Monday, compared to 129 the day before. The Conejo Valley’s levels were measured at 105 early Monday, a drop from 116 on Sunday.

But by late Monday afternoon, the pollution levels dropped to 39 on the coastal shore and 68 in the Conejo Valley.

“They kind of took a dive,” said Doug Tubbs, who manages the county’s air-pollution monitoring. “This time of year it’s hard to predict what the weather is going to do. It presents a real challenge to forecasters.”

Tubbs noted that high ozone levels had been predicted throughout Monday and today. “This is not a happy day for forecasters in terms of being close to the mark,” he said.

Still, Sunday was the first time that the county’s air exceeded federal pollution standards since the smog season officially began May 1. The season runs through October.

“It’s pure coincidence,” Richard Baldwin, director of the Ventura County Air Pollution Control District, said of the way Sunday’s smog seemed to be right on target with smog season.

“The weather doesn’t do something magical on a given day of the year,” he said. “Typically, as temperatures begin to increase this time of year, so do the ozone levels.”

July, August and September are usually the worst months for smog, Baldwin said. Last year, the county violated federal standards for ozone, the main component of smog, on a mere 10 days, making the year the cleanest on record.

But Baldwin said he could not predict what the 1993 smog season would be like, saying it all depends on the weather.

Ozone results when pollutants from cars, industries, power plants and consumer products mix and bake in the sun. Stagnant air traps the ozone close to the ground, keeping it from dilution in the upper atmosphere.

The chemical is a powerful lung irritant, and people with respiratory disorders, the elderly and athletes are especially vulnerable.

Smog levels were still high in the Conejo Valley area early Monday, making it difficult for some people who either had to work or chose to spend time outside.

Linda Kress, a San Francisco resident, looked agonized as she sneezed her way through a golf tournament at the Sunset Hills Country Club.

“Back home my allergies are pretty severe,” Kress said, as she buried her face in a handkerchief. “But here my sinuses are just going bonkers. And I’m on medication, too.”

The high ozone levels had a similar effect across town on Mike Murray, a city landscaper busy working the grounds of Thousand Oaks Library.

“I can feel it in my chest,” he said. “Every time I breathe I feel like I have to cough.”

Others, however, said they didn’t even notice the high ozone levels.