Modern hard drives use fluid dynamic bearings. As long as you keep it spinning, it should be fine. While the drive is spinning, the bearing should be producing enough heat to keep from freezing even if the environmental temperature is well below the manufacturer's spec.
That said, you should use old drives that are out of warranty for this. Although I think you will be fine, the manufacturer would not be amused by out-of-spec operation.
Oh, and drives don't contain desiccant because they aren't sealed. What they normally have is a HEPA filter to trap particles pulled in through the pressure-relief port. It looks like a little tea bag.
Back in the late 90s, I had what I now believe to have been the first in-car MP3 player in Minnesota. It was really just a computer fed into my stereo by hacking the CD changer bus, but still... On a few of the coldest days of the year, it wouldn't boot because the hard drive wouldn't spin up, but it was just a matter of waiting a few minutes for the CPU and PSU heat to thaw out the bearings. That drive survived through several years despite below zero winters and over 100 degree summers.
Sorry.... Totally irrelevant about the bearings.... you have obviously not understood my original posting.
The amount of structural change in the materials over a given temperature range, dictates the reliability of the read/write circuits.
OLD hard drives, strictly recorded ones/zeros onto (maybe in a manchester or other recording system) the media, so they were more reliable over extended temperature ranges, due to the massive size of the encoded magnetic domains.
NEW hard drives DO NOT do this, and the data recovery is based on the probability of the signal recovered from under the noise floor being a one or zero NOT on a hard fact (very frightening but true).
By changing the temperature you change the probability, due to material expansion/contraction, which means data recorded at a temperature outside the drives operating range may ONLY be reliably recovered at that temperature.
