There are several things about a "natural disaster" which usually do not come to mind until the situation is upon us.

Many of us have a more or less formal plan for Disaster Recovery (for the computer center), although there may not be as much done in this area as should be.
Every site should have the ability to recover itself to have data which is at least no more than three days old--counting weekends and holidays recovered within a reasonable time frame.
There should be a written plan with appropriate contacts which will act as a guide if something happens to the data center.
This plan should be exercised at least once a year.

Should be.

Far too many are sloppy about this and this is OK because if you never need it, you don't need it.
There's a lot of slop in the system, so there is latitude to let this sort of thing slide.
Luck is usually on our side.
It's like insurance. If you don't need to ever use it, it's silly to pay for it.

While many businesses may have a Disaster Recovery Plan, most do not have the corresponding Business Recovery Plan.
A few do.
The Business Recovery Plan has more to do with recovering the Business in case of a Disaster than the Disaster Recovery Plan does.
How do you set up your offices off-site if your headquarters is destroyed?
Who needs to be at the phones for plant / customer service?
Who will coordinate and release information about the business?
Who will keep track of employees and how?
What do you *need* to do to get the Business up and going within three days so that it will survive in the short term?
What vendors and contacts will you need to insure communications and continuing business process (fax machines, PCs, telephones, etc).

These and other questions are highly disturbing and annoying, but necessary, *IF* and only if, a Disaster of substantial size were to occur.
It isn't just natural disasters either. Every three months or so, some Misfortune 500 Corporate Headquarters near here is evacuated because of a bomb threat, usually from some disgruntled environmentalist.
Our building is evacuated about twice a year for reasons such as a famous murder trial going on and the threats of violence and / or terrorism.
We take this seriously and have security much like that at the airport.

While all sorts of things might occur, planning should cover about 80% of all reasonable scenarios.

Some other things to think about...

Between Federal Way and Greenlake (about 45 miles) there are 22 overpasses and bridges.
What would happen if people either couldn't get to work for purposes of recovering from a disaster or they couldn't get home?
How do you account for them?
Some businesses have an out-of-state telephone contact at least 1,000 miles away so that messages can be left to account for people whose whereabouts might be in doubt.
Also, messages are recorded to pick up to allow people to know the state of the business in cases of closed buildings, roads, access, etc.

These kinds of planning may take up to two years to formulate.

Finally, each member of our family has a "Disaster Pack" with flashlight, battery powered radio, first aid, blanket and enough food and water to last two to three days, just in case they are needed.  We also have bottled water and canned goods and supplies to last us for a couple weeks, if need be. We have a fire place with enough fuel to keep us warm for several days. Our home was also built with hardi-plank siding (cement impregnated fiberglass) for both energy efficiency and insulation from the elements.

Hopefully, some will find a part of this information informative and useful.