Don't turn them on until notified. Avoid weakened structures, particularly floors, walls and rooftops to avoid structural damage. Do not pump basement out until flood water recedes. If your well has been flooded, assume the water in your home has been contaminated. If you are on public water, your local health jurisdiction will let you know, through local media, if your water is not safe to drink.
Bottled water is the best choice.
If you can, get commercially bottled water that has been stored for less than 6 months in tightly sealed containers. Plan for one gallon per person per day. If the water from your tap is clear- Boil it for 3 minutes to disinfect. If water is cloudy, filter it by pouring it thru a coffee filter and then boil it for 3 minutes. Let it sit for 1 hour.