SHTF to me is a little higher grade of "bad" than a simple ice storm etc...SHTF has to have immediate, life altering consequences.....Just being without heat or electricity in a local area doesn't qualify. If a "Three Day Kit" will get you by....it ain't SHTF! It's a minor inconvenience.
Now, it could be a tornado just hit your house. That's a very serious situation-going to take more than a 3 day kit to recover-that's SHTF. I think an armed gang advancing on your property constitutes SHTF.....as it involves the possibility of immediate death or maiming. Things that could be permanently life altering qualify as SHTF.
The next level is TEOTWAWKI, meaning, the world has gone batshit crazy, no expected police response, critical infrastructure has collapsed- water, electricity, food delivery etc.....This is Madd Maxx kind of stuff.