You can do that so long as nobody else in the area affected by the outage had the same idea and got there before you.
The last major outage (due to an ice event), I hit the stores within the first hour of the outage and they were already cleaned out of water, propane, ice, and getting rapidly cleaned out of other supplies.
The last major outage (due to an ice event), I hit the stores within the first hour of the outage and they were already cleaned out of water, propane, ice, and getting rapidly cleaned out of other supplies.