Trying to figure out how much water you should have on hand as you prepare for a hurricane or other disaster? According to FEMA, you should store at least a gallon a day per person for a 3 day period in disaster preparedness. After having been through more than a few hurricanes, we'd recommend storing a 10 to 14 day supply. If your municipality loses power, or flooding compromises the water system, tap water won't be safe to drink. Sure, water and ice will get trucked in by the government around 3-5 days after a disaster strikes. But do you really want to stand in a 4 hour line for a couple of gallons of water and a bag of ice? (Been there; done that) And what if roads are inaccessible because of downed trees and power lines, or flooding? Or you don't have enough gas and the pumps aren't open because there's a power outage? Water won't go to waste. Commercially bottled water is good for up to 6 months.
And don't forget your pets. The average 50 pound dog will need 1/4 of a gallon per day and a 12 pound cat will need 1/10 of a gallon of water per day.