A considerable body of literature exists regarding what is generally termed "public risk communication." This chapter focuses on best practices with respect to the warning or alerting decision, message content, and message style elements. These elements are described in the context of the steps individuals follow in response to receiving an emergency message. The purpose is to ensure that your emergency messages will be as effective as possible.

The goal of this chapter is to assist you in making the decision to warn, and in composing well written warnings and alerts. Once you have completed this chapter, you will be able to:

• apply understanding of the social context for effective warnings and alerts;
• use Job Aid #2, Warning Decision Tree, to assist you in deciding when warnings and alerts are appropriate;
• write NWEM hazard descriptions to include essential information (who, what, when, and where);
• write NWEM public protective instructions to include essential information (why and how);
• consider elements of style when composing an NWEM;
• use Job Aid #3, Generic Warning Template, as a basis for customizing your own NWEM templates; and,
• plan for monitoring public response.