FRESNO, Calif. (AP) — The San Joaquin Valley is under a new air alert as high temperatures, a high-pressure system and stagnant wind combine to trap smog.

Air pollution officials are asking residents to limit driving and not idle cars while waiting for students after school or at drive-thru windows.

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It’s the third air alert of the year issued by the San Joaquin Valley Air Pollution District.

The district is under a three-year federal fine for violating ozone standards set by the Clean Air Act. So far this year, no violations have occurred.

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The district must record three consecutive years without a violation for the $29 million-per-year fine to be lifted. Drivers are the biggest source of poor air quality and help pay the fine through a $12-a-year assessment.

Officials say the latest alert could last through Friday.

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