Gov. Jerry Brown warned on Thursday of a California ravaged by forest fires, disease and mass migration if lawmakers fail to renew the state's signature program to fight climate change.
Wave of smog is due to settle over the city of 22.5 million from Saturday to Tuesday and levels of PM2.5, the smallest and deadliest airborne particles, are set to top 500.
Schools suspended outdoor activities and polluting factories ordered to cut production as thick smog cuts visibility was cut to several hundred meters.