Found this explanation,quoted from the writer:
Listen carefully—that's eight short blasts. I asked a NorthWestern Energy worker what catastrophe would trigger such a warning. Dam failure, he said. Of course. This was on Ryan Island just downstream of Ryan Dam. (Ed Kemmick/Last Best News)
It doesn't have to be a failure, sometimes just opening a spillway is enough to flood certain islands. I've seen a video (probably Tom Scott, but not sure) of a dam where the spillway is opened every day to show tourists what the downstream river looked like before it was constructed.
I know what you're thinking: "Did he hear eight blasts or only seven?" Well, to tell you the truth, in all this excitement I kinda lost track myself. But being as you're supposed to evacuate the area, you've got to ask yourself a question: "Do I feel lucky?" Well, do ya, punk?
Over the years I’ve collectively heard six short blasts. Two more blasts and I’ll have the full set and need to start evacuating.
The place where I work has an emergency alert public address system. I heard them test it once. It sounded a bit like the first part of the tripod sound from War of the Worlds:
I think it wouldn't take more than a couple blasts from that before I'd evacuate something.
One of the creepiest real things like this that exists is Chicago’s tornado warning siren
Unfortunately they don't use the "Alternate Wail" signal in the video anymore. A few years back they switched to standard Wail.
While we’re all wondering what happens at 7 or 9 short blasts, I’m asking how a blast could even be long.
What is this for? I think it says NorthWestern Energy but am not sure. If that's right, maybe it is under a dam's spillway and they use eight short blasts to announce a release of water?
Whenever Im in this situation I just float up to around 1000ft and wait for all the screaming to stop before coming back down.
8? Are there other codes for 7 & 9, that we need to be counting? What if we were sleeping and unsure of how many blasts we heard? :)
Where are you running to? It's an island
E: Nevermind, I'm an idiot. You're probably running to a boat or something lol. Have a nice day
Why? There's plenty of time. If there was any danger at two blasts, they would have said so! You can hang out for a bit longer no worries.