Originally Posted by Mr_Gone
I haven't found anything specific regarding how d3O armor protects when it's cold, but I believe it was originally designed for snowboarding and skiing applications. Seems like they would have considered that these sports occur during cold weather.
Then again, maybe I'm assuming too much.
I'm thinking in a fall, the main thing is abrasion protection of things like knees, elbows, shoulders where the skin is thin and joints are protruding. Some absorbtion of impact is there too, but that's secondary even for foam padding. Even if the stuff did crack when cold on first impact, it's usually in a tight fitting pocket that would hold it in place for the few seconds of a slide and it would probably still provide reasonable protection.
The main take-away for me here is being extra careful (or not to mess with) removing the pads from the pockets when they're really cold to avoid a problem. I have bent and removed pads when they are quite a bit more stiff than room temp, but have never seen them crack or been concerned they would. But I bend them slow and don't force them. I'm confident enough in the material that it will work when I need it most.