Card networks, ATMs, and apps fail when communications or power fail, even if the grocery store is open and the clerk is willing. A modest amount of cash in small bills is not a survivalist affectation. It is how you buy ice, fuel, or a ride in the first day.

The failure is ordinary. The card reader needs a signal. The ATM needs a network and a vault that still dispenses. The store may have the lights on a generator and still be unable to run a chip card. Cash does not ask the network’s permission.

Do not make it your life savings in a drawer. Make it enough for a week of the things you cannot store — fresh gaps in the plan, a prescription co-pay, a tank of gas if the pumps have a generator.

Small bills matter because nobody wants to break a large note for a bag of ice when the register is a notebook. Ones, fives, and tens are the denominations of a manual economy. Keep them dry, and do not spend the envelope on a calm Tuesday so it is empty when the reader is dead.

Pumps, pharmacies, and a ride are the usual first-day purchases because they sit outside the pantry. You already stored the rice. You did not store a trip to a clinic that still has power, or the co-pay the pharmacist still has to ring by hand.

Agree in the household where it is. A secret stash nobody else can find is not a family plan.

Tell the other adult. If you are the only one who knows the drawer, the plan ends when you are across town. A shared place, a shared amount, and a rule that it is replaced after it is used will outlast a clever hiding spot.