U.S. test of national alerts on Oct. 4 at 2:20pm EDT (1820 UTC)

Sun Oct 1 22:24:12 UTC 2023

This year's test of the U.S. national emergency alert includes something 
for ISPs and network operators.

The wireless portion of the national test is scheduled 2 minutes (2:18pm 
EDT or 1818 UTC) before the main broadcast test at 2:20.  Mobile phones 
usually receive the alert about a minute later. Radio and TV will receive 
the national alert a few minutes after 2:20pm.

iPhone iOS 17 added a new feature for Wireless Emergency Alerts. When iOS 
17 iPhones get a wireless emergency alert (WEA), it will trigger a data 
network query for additional information.  Its a small query and 
response, but there are a lot of iPhones making the query at the same 
time (I'm assuming Apple engineer's have built in some time skew).

Apple has assured FEMA that Apple's CDN and servers will be able to handle 
the triggered load.

The iOS 17 triggered query will either be a tiny blip in the network 
graphs around 2:18pm to 2:22pm which no one will notice, or some CDNs and 
ISP operators will be wondering what that heck that spike was.

If your phone is configured with Spanish, it will display the alert in 
both English and Spanish.

“THIS IS A TEST of the National Wireless Emergency Alert System. No action is 
needed.”

“ESTA ES UNA PRUEBA del Sistema Nacional de Alerta de Emergencia. No se 
necesita acción.”

You'll know your iOS17 device did an extra data query, if it displays a 
longer message (extra sentences) in addition to the messages above.

"This is only a test. No action is required by the public."

https://www.fema.gov/press-release/20230803/fema-and-fcc-plan-nationwide-emergency-alert-test-oct-4-2023