I have a 14-day supply of freeze-dried food under my bed. In an emergency, finding sufficient water to reconstitute it would be the main concern.
But three days? Like, what is that accomplishing? I decided to go off grid after the 2021 ice/snow storm wherein the Texas grid nearly collapsed. Some in Austin retained power the whole time (helps to live near a hospital), while load shedding forced the rest of us to go without power for a week.
We didn't get anywhere near to above freezing for days (highs around 18F/-8C). I survived by boiling ice and snow on my gas stove that I had to light with a match at that point. I was able to maintain indoor temps above 40F/4C that way and had sufficient blankets to survive, but this is not a standard threshold.
One starts to rethink reliance on the grid at that point.