And it seems as if--at least now, in the San Gabriel Valley--anything that’s other than hot and smoggy is an anomaly.

Last Tuesday, on what may have been the smoggiest day of the year, Joe Cassmassi was talking about air quality.

“It’s a strange time of the year,” he was saying. “Most people think that because we’re heading towards winter, that we should have improved air quality.”

That sounds reasonable. Just like white shoes, right? No gray or brown air after Labor Day? “(But) we find we’re in a transition. We have less ozone in the air, but more nitrogen dioxide.”

All-season smog? Say it ain’t so, Joe. What about that nice rain we had a week and a half ago that made the air so clean and clear for a couple of days?

“This time of year, it’s more of an anomaly to have the storm than it is to have the high pressure” that traps smog near the ground. “One day will be pristine, one day very smoggy . . . it just demonstrates how capricious the weather is in this area.”

Anomaly is one of Cassmassi’s favorite words. In talking about weather, he uses it about every fifth paragraph. And it seems as if--at least now, in the San Gabriel Valley--anything that’s other than hot and smoggy is an anomaly.

Cassmassi knows a few things about the fickle finger of smog in the San Gabriel Valley. A senior meteorologist with the South Coast Air Quality Management District, he’s spent half his professional life, seven years, in the district’s El Monte office.

What all of us--natives, longtime residents and recent arrivals--are forgetting, he says, is how far we’ve come: “Air quality now is a hell of a lot better than 10 years ago and significantly better than 20 years ago. People have a tendency not to remember a long, long time ago.”

With auto emission controls and other measures, “we’ve made significant progress in controlling smog.”

Just look outside, though, and you can see it’s not enough. The final assault, Cassmassi says, will take modification of life styles, modes of transportation.

The first phase of AQMD’s three-tier air quality management plan that’s designed to clean us up by 2007 is set to be in place by 1993. It will require, among other things, most paint solvents to be water-based rather than oil-based; improved vapor recovery on gas station nozzles; lower emissions from medium and light trucks; particle traps on diesel buses to catch soot before it goes out into the atmosphere.

If the plan works, Cassmassi says, “we hope to eliminate first-stage (smog) alerts by the year 2000.”

That’s great. We all hope it works, and we’ll try to do our part. But what about now? Smog is cumulative--worse at the end of the summer than the beginning--right? So how did it build up so fast after the rain?

What happened, Cassmassi says, is that “two phenomena”--Hurricane Octave off Baja and an ocean storm to the north--met in Southern California. Though Octave was but a tropical depression by the time it got here, it was still enough to cause the moisture.

The two storms battling not only brought the rain, but also opened up the upper atmosphere, allowing the smog to escape. Voila ! Clean air.

“The storm was an anomaly,” Cassmassi says.

But when a storm leaves, “high pressure builds up again, typical of Southern California in September and October, (and) in the wake of this storm you had pseudo-Santa Ana winds . . . just strong enough to keep the sea breeze from cleaning (the air) in the late afternoon.

“Storms go west to east, following the jet stream. They allow high pressure to build, favoring the Santa Anas. . . .

“It doesn’t take very long to get some very high levels of smog. Only a day or two.”

More on the good-news-means-bad-news front: drive-time blindness. Around the autumnal equinox, or first day of fall (Sept. 22), the sun is low in the sky, right about at the horizon at drive time. Usually, smog helps to scatter the sun’s white light when you’re driving right into it.

But clearer air from the storm meant many commuters were either staring into the sun or having it reflected from the cars in front of them when they were going to or coming from work.

Bottom line: After a few days of clear weather, you get a lot more hot and smoggy. A little enjoyment, a lot of remorse. Sounds vaguely biblical.

“It makes for interesting weather forecasting,” Cassmassi says.

Forecasting? So tell us what’s coming up, more of the same?

Well, the recent storm, Cassmassi says, was an early harbinger of late fall and early winter. “Winter storms (can start) as early as the end of September, as late as the middle of December. But generally, around mid-November we’ll see the onset of classic storm systems penetrating through Southern California.

“One can envision a storm track as following the sun, higher in summer, lower in winter. . . . As winter comes on, less intense sunlight allows the storm track to dip south.”

OK, that’s why winter happens. But what about next week?

“There’s a storm system working its way down the West Coast, not as strong as last week. We don’t anticipate rain. We expect the weather to clear out into weekend, then repeat the pattern.”

That is, more high pressure and “barring a full-fledged Santa Ana,” more smog.

But here’s some good news. This year, Cassmassi says, the San Gabriel Valley had the cleanest August since AQMD kept records. Whereas there usually are 15 to 20 first-stage smog alerts in August, this year there were only four.

Or, as Cassmassi put it, “It was anomalous.”

So that’s it, the last word from the AQMD’s new resident philosopher on smog.

To be sure, Cassmassi, a modest man, would hardly claim such a title. Agency spokesman Tom Eichorn suggested Cassmassi when asked for a thinker on smog, after hesitating a moment. “We used to have somebody to talk about it,” Eichorn said, “but he moved to Seattle.”