Weather Underground only reports ozone pollution at your link...ozone pollution is primarilly a summer problem (Sun/Temp. acting on NOx/VOC's). The winter pollution problem is primarilly "PM 2.5" (smoke)(particles around 2.5 microns in dia.) in inversion areas (especially the central valley of Calif.).
http://www.wisegeek.com/what-is-ozone-pollution.htm
http://www.valleyair.org/aqinfo/forecast.htm