In the past, during the really hot days, local gov'ts used to provide "cooling centers" for those who couldn't afford to cool their houses or for those who were "homeless." I'm not sure what the solution will be if PG&E turns off power to a whole town/region as there will be no power anywhere for these cooling centers to operate. My best guess is that the local hospitals will be the only places to go in the event of a power shut-off since they have back-up generators. I imagine it will get very warm and uncomfortable in these locations as the systems try to compensate for the additional body heat generated by masses of people seeking someplace to cool off.
Some people may be able to stay with friends or relatives who have generators or live out of the area. People who are dependent on power to run medical equipment at home - oxygen, CPAP, etc - have been urged to purchase a generator or a battery back-up system for their devices. :/ If you can't afford it, oh well, they warned you! You are also encouraged to NOT keep lots of food in your freezer or fridge -- exactly the opposite of what a good prepper does. :/
No power also means (probably) that restaurants and fast food places will not be open for business, so there will be no way to get a hot meal. And how will the refrigerated and frozen foods in grocery stores and convenience markets hold up to no power? I have no idea if any of them have back-up generators or not.
When I was a child we used to cool our houses by opening the windows and doors and running fans. But without power there won't be any fans! HOW did the people who settled this state live and handle the heat prior to electricity???