My water usually does not freeze, no doubt due to relatively mild NC winters. They last several days of below-freezing weather behind the seat of my truck.

I tested a Nalgene 1000 ml water bottle in my freezer and found that you can freeze it solid without ill effects if you fill it no more than 900 ml.

I use Nalgene bottles, plus one stainless. I've learned from experience that typical bottled-water bottles are bad for long-term vehicle storage. The vibration of driving can wear a hole through the thin material.

Regarding the larger thread topic, I generally try to wear or have ready access to whatever I would need to spend the next 24 hours outside. That usually translates into wearing a slightly heavier coat than the daytime weather requires, with a knit cap in one pocket. I also try to be prepared to walk home from work.

Regards,
Steve