Why does emergency alert go off

Alexandertuttle wrote:

Why dose the tornado alert goes off for a test in the middle of the night in Nebraska

Start here: About emergency and government alerts on iPhone and Apple Watch - Apple Support

There are currently tornado watches in your area; the United States National Weather Service has issued tornado watches in Nebraska and Kansas, and your iPhone is configured to receive those from your carrier.

https://www.spc.noaa.gov/products/watch/ww0158.html

https://www.spc.noaa.gov/products/watch/ww0157.html

The current convective outlook is nasty, too:

As for a late night test, that would be unusual and best check with your cellular carrier and maybe with NWS.

Nobody here would know. Ask the organization that creates/sends the alerts.