Don't be surprised if your phone (and everybody else's) goes into a panic in the near future -- that's on purpose. FEMA and the FCC are conducting a national test of both the Emergency Alert System and Wireless Emergency Alerts on September 20th starting at 2:18PM Eastern. If you're included in the test, your device will receive a tone and a "Presidential Alert" warning that makes clear this is just a dry run. You can't opt out, and if circumstances make it inappropriate to send an alert, the test will be postponed to October 3rd.
This isn't the first nationwide EAS test, but it is the first for WEA -- it'll be crucial to showing that the mobile-oriented system can work as effectively as conventional TV- and radio-based alerts on such a large scale. And to no one's surprise, FEMA and the FCC are taking great pains to notify people in advance and avoid the chaos that stemmed from Hawaii's false missile alert.
In some ways, the test might be a sign of things to come. Senators recently put forward a bill that would reduce the chances of false alarms, add alerts to streaming services, eliminate opt-outs for some federal-level notices and repeat alerts coming from either FEMA or the President. Simply speaking, these kinds of tests may be more frequent and widespread.