Catastrophic flooding is occurring in Central Texas this morning.

[BeyondKnowledge]

If I sleep with my cell phone off are these warning systems able to ping it and sound an alarm through it anyway?

Some say they can turn on cell phones but they won't admit it. Why turn off your cell phone? Just mute the calls and texts. The alerts will still get through. 

I do know all cell phones are capable of calling 911 without a subscription to a service andd. That is a law.

There are some reports that cell service is spotty in some of the hills of that area. That is on the local governments. They should have not allowed those companies to put the service there if it did not cover the whole county. That should have been part of the contract for full coverage for cell alert service.

And like I have already stated, each campground should have had a night fire guard on watch patrolling with a cell phone. The National Weather Service alerts would have been noticed that way.