Wow. The information, comments, conjecture, and 'facts' in this thread are definitely entertaining. Some are downright hilarious.
To clarify a few different points, so-as-to muddy the waters somewhat AND get all ironical (see what I did there?), ya'll need to know that there are two COMPLETELY DIFFERENT styles of "hose-bib" sold on the market. There is the "internal shut-off" style made for cold-weather climates, and the "external shut-off" style made for balmy tropics which starts at the Canada/U.S. border and continues south.
Definitely not "all" hose-bibs are the same. So be careful with that statement AND checklist.
"moving water doesn't freeze"..... uh huh. Yup. That's a fact. Except for every river, creek, crik, and slough. They ALL freeze, to one extent or another. Now, to help explain matters, there is the ratio of "volume" and "velocity" and there is a whole set of criteria that match up with that. Couple that with 'temperature' and it gets complicated'er.
Metal will freeze. Water inside metal will freeze. The colder it gets, the more the molecules 'expand'. When that expansion overcomes the metals plasticity, then you've got a break. It's up to you to run the numbers, OR the odds, and see how it plays out.
The water supply lines to homes in this city are between 6 and 8' down from grade. There are MANY houses each year, that have 'frozen water lines'. Yes, that is water supply lines. I won't even get into the electri-magical methods that they use to thaw those lines. But, a 'temporary' fix is to run a garden hose from your NEIGHBOR'S hose-bib, AND you have to leave a faucet in the house running with a constant stream 'just a touch more' than drips. And yes, that can (and does) work for a few months, until Spring when the problem miraculously "goes away".
There are many different ways of plumbing a house. Those ways have changed over the years/decades as the BUILDING CODES have changed/adapted to newer methods, better materials, and other factors as well.
When the answer from someone starts with "You could just....."
Don't.
Run away while you still can.
And yes, I have 2 pairs of snowshoes downstairs, in the 'just in case' pile. Actually, 1 pair of snowshoes and 1 pair of 'bear paws'. There's a difference.
For when the power is out, here, we do have contingencies, secondary contingencies, as well as redundant contingencies. I'm thankful that we've never had the power out long enough that we need to entertain the redundancies,,,, but there's still there if needed.
I'll be not many here are even going to have a clue about 'electric roofs', right? Matter-of-fact, I just unplugged ours today. And yes, the "building codes" that enabled the necessity for that need have been improved and changed, to which construction nowadays (when done properly) do away with the need to have an electric roof. Ain't that gooder? At least it stops the indoor rain in the winter.
I hate having to need an electric roof, but I sure am glad we have it.
Have fun, play with that, enjoy, and right now it is -24/-32 outside.