I was reading an article on the recent tornado in Missouri and was struck by the comment of one of the victims. He talked of how they had heard the warning sirens and had gone outside to look but saw nothing so they took no action. When the sirens sounded a second time, it was too late for him to seek shelter.
Unfortunately, this is not uncommon. I've blogged elsewhere about the hesitation of local officials to sound warnings but it's worth noting that even when they do so in a timely manner, the public doesn't always react. We've got a considerable amount of research showing that people no longer trust official warnings. Instead, they seek verification from other sources, usually within their circle of family and friends.
The lesson for crisis communicators is obvious. We can't assume that because our message has been released through the media that people will act on it. Instead, we need to make sure we are using multiple sources, especially those used by people to communicate with each other. We need to be part of the conversation.