Today I read that an invasive type of spider is spreading in California. Although it is not as dangerous as a Black Widow, it can cause a painful bite that can lead to a serious infection if not treated right away. These spiders build webs closer to human activity so will be more likely to come into contact with people and thus more likely to bite them.
This link is about the current invasion that Europe is experiencing, however California is having it's own invasion as well. There has been a case or two of them in Sacramento, but the larger invasion is on the southern California coast. It is called an invasion because these spiders are native to the Canary Islands.
They are thought to have been transported by potted plants and other means.
Wipe down any webs around your house, inside and outside. Spray around the outside of your house and inside cabinets and under furniture. And if your child or other family member gets bitten, wash the area with warm soapy water right away and see a doctor if it starts to swell. Better to be safe than sorry.