Hurricane Matthew is barreling toward Florida on Thursday as a massive Category 4 storm, and officials are telling 2 million people living in evacuation zones to get the hell out of the way. “This storm will kill you,” warned Gov. Rick Scott.

But in any dangerous storm, there are always people who won’t flee. They’ll recall a storm in the past that wasn’t so bad, or they simply don’t want to leave. Emergency managers have a whole series of best practices to cajole these folks to go.

But the tactic that has always stuck with me is this one: Officials will tell residents who refuse to evacuate that they should grab a permanent marker and write their Social Security numbers on their arm — so that police can identify their bodies after they die. Here’s a haunting quote from a New Jersey resident after Sandy in 2012:

“The reason I got scared (was) Gov. Christie began telling people to put their Social Security number on their arm so the police could identify the body,” Kooperman said.

In a similar vein, other officials will ask recalcitrant residents to fill out paperwork for notifying their next of kin. Or emergency managers will warn that if anyone stays, it will be too dangerous for responders to rescue them. The whole point is to make the danger vivid and concrete. This storm will kill you. Many meteorologists are trying that now with Hurricane Matthew:

If you stay in #Matthew evacuation zone, it will likely be one of worst decisions of your life. May also be last decision you'll ever make. — Gary Szatkowski (@GarySzatkowski) October 6, 2016

That said, while fear tactics can be powerful, they don’t always work. As Christopher Mele of the New York Times points out in a fantastic piece on how emergency managers try to convince people to leave, about 5 percent of residents typically end up staying behind, no matter how much officials plead. Fear can be powerful, but so can inertia.

Read more: The immensity of Hurricane Matthew, as seen from space