Are you sure they weren't getting Severe weather and flooding alerts from their weather apps? I get emergency alerts (mostly Amber alerts), but the severe wind, rain, hail, flood
and even hurricane events I get are all from my weather app (I'm using
AccuWeather). Yes, FEMA does send out alerts, but NOAA, "the weather bureau" generates the weather alerts. The
NOAA Alerts or
CellularOne CMAS app should give you more of what you want. (Or Google
noaa alerts - you can sign up for email or text alerts.)