Morning Fog Becomes Summer Smog

In yet another display of tenacious late-summer weather, thick fog enveloped much of the Southern California coast Tuesday and, by midday in some places, fog became smog.

“It’s sort of like summer’s last gasp,” said Joe Cassmassi, senior meteorologist with the South Coast Air Quality Management District. “This should be the last day of the real murky conditions.”

Before sunrise, visibility was a mere 1/16th of a mile in El Toro in Orange County and a quarter-mile at Point Mugu in Ventura County. By 9 a.m., with coastal temperatures around 60 degrees, the morning sun was slow to burn away dense fog in many locations. Visibility was only a quarter-mile in Santa Ana and a half-mile in Santa Barbara.

The foggy weather was evident in Tuesday’s relative humidity readings, which ranged from 26% to 100%.

Despite the early morning murk, ships charted their way uneventfully through Los Angeles Harbor, planes took off and landed relatively on time and freeway traffic chugged along--although more slowly than normal.

The National Weather Service issued traffic advisories on the hazards of fog early Tuesday, but the California Highway Patrol reported no more accidents than usual in Los Angeles, Orange and Ventura counties.

The foggy weather turned to smoggy weather, however, triggering pollution advisories from the South Coast Air Quality Management District. Conditions worsened into the “unhealthful” range in the Santa Clarita Valley, eastern San Bernardino County and Riverside, where temperatures ranged from the upper 80s to upper 90s. And in Pasadena, where a first-stage smog alert was declared, the air was even worse.

Tuesday’s high at Los Angeles Civic Center was 81 degrees with an overnight low of 60.

The hottest spot in the nation was Borrego Springs, east of San Diego, where temperatures reached 109 in mid-afternoon. Palm Springs, which reached 108, recorded 100-plus temperatures for the second day in a row.

However, meteorologists say the unseasonably high temperatures should drop several degrees each day in the coming days.

A low-pressure system is expected to replace a strong high-pressure system, which has been sitting above coastal areas and has “squashed low clouds down to the surface,” said meteorologist Steve Burback of WeatherData Inc., which provides weather forecasts to The Times.

This new system, he said, not only will bring with it lower temperatures, but less fog and smog.