Most of us have multiple ways to receive warnings for tornadoes, hurricanes, flooding, etc. Most of these events are defined by specifics, such as the minimum requirements to define a severe thunderstorm (warning). it's defined by the NWS as "hail of 1 inch in diameter or larger, wind gusts of 58 mph or greater, or a tornado." One of the warning systems we have is on our phones and is a known as the Wireless Emergency Alerts (WEA). It's a mandated federal warning system and includes several events to include weather.
The warning is transmitted to the areas of interest and the individuals receive the warning via text message. Your phone must be WEA - capable and activated to receive the warnings. Your carrier must also participate in the program. After a brief search regarding the WEA, I found the WEA system is "selective" on warning parameters. For instance, back to severe thunderstorms. IMO and most all meteorologists, a severe thunderstorm is just that. But the govt carries it further and has an additional category known as a "destructive" thunderstorm warning. The "destructive" tag on a severe thunderstorm warning indicates a higher level of threat, with expected wind speeds of 80 mph or greater and/or hail of 2.75 inches in diameter or greater.
I have had tornadoes with never a warning from the WEA system. That's with 2 phones. Friends and family have never received the WEA msgs. I do have weather radios which are reliable as well as a warning system from my county sheriff's office (NOAA - Based) and local tv weather apps. I use Pure Talk, which is a Mobile Virtual Network Operators (MVNOs) associated with AT&T. I contacted them and they assured me they are a participant.
My whole point being a couple of points actually. WEA using a messaging format. Fine and dandy. But if I've never had a message, I can't set the notification parameters such as silent / sound, type of sound, volume of sound. No reason for me to believe the flooding victims had anything different. Found the following on wiki: When the alert is received, a sound is played even if the ringer is off. On nearly all devices, the
Emergency Alert System radio/TV attention signal sounds in a predetermined pattern.
Seems like one time I received a "National" test warning and it was blaring. I have never received any test warning since. I suspect many of the good people in Texas experienced similar lacks of warnings reaching their cell phones.