"Presidential" "head of state" alerts (other countries call it something different) are the most severe type. It often involves something like nuclear war. I think sometime ago Hawaii got a huge glitch in their alert system and infamously warned all their people an incoming ICBM was heading their way.
Yet another reason I'm not a fan of emergency alerts. I've been woken up at 2AM for a lost child three states away too often, and in January 2000, we never got warned for an EF3 tornado until a few minutes after the storm had ended. It was the black sky at 3PM and power failure that alerted us.
I never rely on any government for any kind of safety. My state, Kentucky, insists that every half inch of rain is a flood (they never saw Katrina aftermath to know what a real flood even is) and incessantly warn for river flood warnings. Yes, even with talking sirens usually meant for tornados. There's so many false positives and negatives to not put any trust into our EMS alert system. It's horridly out of date.