Quality when it comes to laptops is a variable that is best applied too "to each there own.." basically your mileage may vary on what hard drive is best as it certainly does for those that buy them..
I favor seagate cause all there drives have 5 year warranty's.. I think there owned company maxtor has 5 year's to but I digress I have general dislike of maxtor even if now owned by seagate.. I also own a few WD's raptors cause those are the rare few that have 5 year warranty's..
As suggested I would recommend a laptop drive if space is not a issue.. if space is a issue anything will do.. there are some rare 7200 rpm laptop drives in some hitachi usb cases out there too
As for leaving it in the cold, I think in real world practically you should be okay.. but you can check the website for the manufacturers and read there spec's.. (sorry don't have super useless info memorized) there more then likely say something like no more then 20-40 F but as I said real world you're likely fine.. as I have honestly placed quite a few drives in freezers.. (geek trick)
Your worst case scenario in data loss is only 2 things.. as I say frequently..
1. Worse virus in the world.. wipes every drive in your computer
2. Fire/Lightening/Earthquake or physical damage..
In these scenario's it's best too..
1. Keep your data backup drive Unplugged unless backing up.. or if you have 2 one should be unplugged..
2. Place it in a fireproof safe or take the backup offsite as major company's do..