When I was in charge of 120 marine supply strs the instructions were:
1) Take cash and hand write CC's. Each str had a pad of special receipts to do this or hook up one register to a marine
battery and inverter. Not all of my strs sold invereters due to their cost. If CC's were hand written, then to enter the
CC when the electric came back on.
2) If you didn't know the customer (s) allow customers to shop in small groups. A good ratio was 2 customers to each
in store associate. Many of our customers we knew by first name basis.
3) Keep the door locked and let in/out customers as needed.
4) Stay open till further notice. Of course back then we were not talking about EMP just plain old power outages so cell
phones were still working. Most earlier stores also had one hard line phone that needed no electric to run. That phone
was kept under the front POS counter.
Having stores along the coast this did happen frequently.
During hurricane season we had pallets in our east coast warehouse, packed and shrink wrapped ready to go in a minutes notice.
There were two type of pallets packed. One was for pre-storm and included many things customers would want, e.g. 1/2 - 1" nylon line,, batteries from AAA on up to Group 27, flash lights, chain, gas cans, coolers, etc.
The post storm pallets included: A Generator, more gas cans, Group 24 & Group 27 deep cycle marine batteries, more coolers, inverters the most popular were the 1200 Watt ones, 12 volt fans, 12 volt bilge pumps, propane bottles, etc.
Post the storm and when the airport was reopened, the VP for the region would fly in to assess the situation and offer morale support.