I planted canna in a spot in my yard last year. I don't think it's ideal for them because I didn't get good return then and I'm not this year either. More are coming up still though so they may just be late. The slugs might have got to them too though.

I have never had any winter over here that were not in my heated greenhouse.

I've lost them in my shed, garage and huddled together and tarped on my back patio. All before the greenhouse or when it was full.

In ponds, they usually won't tolerate being submerged in winter except for the Longwood hybrids which are more aquatic than garden hybrids.

Record breaking cold temperatures in December are not conducive to canna lily survival. Sure the rest of the winter was mild, but tender stuff was already dead!

then there's the cool spring, which would have slowed growth of any survivors. And the slugs love cool springs so there would have been lots of slugs to eat the little bit of growth. Then no heat this summer to get them really growing.

And despite being sold as pond plants they don't like being submerged, so cold wet soil in winter will do them in in no time.

three strikes and they're out. Cannas are not perennials around here.

i have a neighbor that has some planted along the north side of her house, along the foundation. they survived the last two tough winters. there is a bit of an overhang above them, so they might not get full winter moisture.

For the past 5 years I have kept pots of cannas on a covered deck. The hard freeze in December got all of them except one large rhizomes of a Tropicana.
I had left them near the edge of the deck and with all the rain, then the freeze, they were history.

Plants in exposed pots may be as much as 20 degrees F. less hardy than the same kinds would be in the ground, this pattern has been observed using a variety of kinds in organized experiments. Pots sitting on the soil benefit from contact with the warmth of the earth through the bottom of the pot. A pot up in the air on a deck is liable to experience maximum exposure to cold, unless it is surrounded by insulating materials before freezing occurs.