First, DEET: apply insect repellent that contains DEET, oil of lemon eucalyptus, and others that would help insects and mosquitoes to be avoided.
Second, Dawn and Dusk: since the mosquitoes are most active during the morning and the evening, it is important to wear protective clothes and keep the doors and windows shut.
Third, Drain: Mosquitoes use stagnant water to lay their eggs. Drain all areas where there is standing water, including buckets, old tires, gutters, birdbaths, and pet bowls.
Above all, there are no incidences of malaria, West Nile virus, or St. Louis encephalitis virus have been reported in humans, and with the incoming colder seasons, this disquiet will hopefully abate soon for the residents of California.