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.
If there is no one in sight in FRONT of you, and a line of assorted vehicles BEHIND you, it is NOT because they always wanted to be in a parade. — Florida Lime.