The California Department of Social Services clarified this in a 2015 memo to the county welfare directors (PDF) about residency requirements for the CalFresh program.
In the "Out-Of-State" section, it discusses the procedure to be used when a county discovers that one of its clients has been accessing their benefits in another state:
County A receives an EBT usage report indicating that a client has been accessing their
benefits in another state for an extended period of time. The county must attempt to
contact the client by sending an RFI to the last known address to determine if the client
has moved to the other state or intends to return to County A. The household responds
stating that they are temporarily in another state caring for a sick relative, or fleeing
domestic abuse, or any other reason, but intends to return to County A. As long as the
household continues to meet its reporting requirements, County A shall maintain the
case. However, if the household has not returned to County A within one year, the
household will be considered to have changed its state of residency and must be
discontinued. No notice of action is required. If the client does not respond to the RFI,
the county should take appropriate action as described in MPP 63-300.5 (a)(2).
Basically, the county will send you a Request for Information (RFI) that you will need to respond to, asking you if you have moved away or if you intend to return. If you respond that you are only away temporarily and give a valid reason why you are away, your benefits are supposed to continue, as long as you return to your home within one year. If you fail to respond to the RFI, or if you fail to return to your home, the county will terminate your benefits.
Hat tip to @mkennedy for posting about this memo in the comments.