Everyone should keep some emergency cash. The amount is up to the individual. Only the individual knows what they feel is enough.
After the most recent hurricane landfall in the Florida panhandle, electronic cash was just out of the question. Some retailers did open using generators or simply opening the front door selling food items, water, and similar items… but for cash only!
Should a bank “holiday” occur, having cash will keep you going for a while. Where and how you decide to secure it your business. I wouldn’t post how you do it.