The devastating wildfires in Northern California are having an impact on air travel in that part of the country. ATC delays may be impacting your travel. If you are scheduled to fly through SFO you will want to contact your airline to see if there are active delay programs in progress.
If your flight is delayed then ask about alternate routings to get you to where you need to be.
The airlines are changing tickets without change fees due to the delay conditions.
Don't get stuck with a long delay if you don't have to.