Simi Air Quality in Unhealthful Range

Despite blue skies and visibility of 16 miles, Simi Valley’s air was unhealthful Thursday and expected to remain the same through Saturday, air quality officials said Thursday.

A high-pressure weather system that trapped pollutants near the ground combined with temperatures in the 90s to drive air quality to 113 on the Pollutant Standard Index Thursday. Anything over 100 on the index is considered unhealthful.

The same weather pattern and even higher temperatures that could reach into the low 100s today were expected to keep the pollutant index at 110 in Simi Valley today, said Kent Field, meteorologist with the Air Pollution Control District.

Similar conditions in the Ojai Valley put air quality in the moderate range at 77, Field said.

“We have light winds, hot temperatures and a high-pressure system with descending air that holds pollutants low to the ground,” Field said. “That’s what’s causing the problem.”

Along the coast, the cooling effect from the ocean kept temperatures lower and ozone pollution down at 53 on the index, he said.

By late Saturday, a new weather system is expected to move in, bringing cooler temperatures throughout the county and causing smog levels to fall back into the moderate range in Simi Valley, he said.

The coastal cities will continue to have night and morning low clouds and fog, he said.