California is home to 7 different species of Rattlesnakes (including subspecies, there are 12 types of rattlesnakes), and their population has been booming. While climate change is overwhelmingly negative for many species and the earth as a whole, some species are able to exploit the change. Rattlesnakes in CA are content with temperatures of 70-74, but prefer their body temperature at around 86-89. Higher temperatures due to climate change will increase their activity and habitat range, which will be most profound in Southwest CA.
Cal Poison provides general tips on how to avoid fatal confrontations with rattlesnakes and what to do or not do if bitten (get immediate medical help!). There’s also advice (via Contra Costa) on how to prevent them from getting on your property. Because of the danger rattlesnakes can pose to domestic animals and humans, one may want to contact animal control for their removal. It is worth noting that you can legally kill/take rattlesnakes (except for red diamond rattlesnake) on your property, though with a daily bag limit of 2 per person, if that’s your cup of tea.