You must evacuate if you live on a barrier island, in a low-lying area or in a mobile home.

Otherwise, your first choice should be to stay put.

If a major storm threatens South Florida, it could take up to 99 hours to get everyone out, studies show.

That’s more than four days for perhaps millions of evacuees from Miami-Dade and Broward counties to go through Palm Beach County and northward. But authorities typically don’t know a storm’s power or direction that far in advance.

Four days before landfall, Hurricane Andrew was an ill-defined, weak storm far out at sea. Emergency managers don’t want motorists stalled in bumper-to-bumper traffic as the hurricane comes ashore.

You should not stay home if you live in an evacuation area.

IF YOU STAY HOME

Make sure your home is as reinforced as possible.

Consider the house’s condition and whether your family is healthy enough.

IF YOU STAY WITH FRIENDS, RELATIVES

Make arrangements far in advance. Check again as the storm approaches to make sure your hosts aren’t on vacation or renovating.

Take same things that you’d take to an emergency shelter.

IF YOU USE A SHELTER

Shelters should be used only if you’re ordered to evacuate and have nowhere else to go.

Use this site now to find the nearest shelters. Some will fill up quickly, and some won’t open at all.

If you need transportation or special help, make arrangements now.

IF YOU LEAVE THE REGION

No place in Florida is safe from a storm. It could envelop much of the state or march up the coast and turn toward your destination. In 1995, Erin threatened Miami, and thousands fled to Orlando, where Erin struck.

Decide your destination and get a hotel room before you go. Rooms fill quickly.

Flying may not be an option. Airports will close well in advance of the storm.

Trains will fill quickly and will stop running once conditions deteriorate.

Check your car. Fill tank, check tires, fluids and brakes. Get a current map of backup routes.

Leave early.

If roads are already jammed, go back home or to a shelter. If the storm is 24 hours from landfall or closer, it’s too late to try to leave town.

Tell someone where you are going. Leave a phone number.