I don't normally do this, but last week I left the gear in the car overnight in the attached garage - laziness on my part, really. Anyway, the overnight low was only about -6 outside, so I figured it would be okay. So, on the following day's gig the screen on my keyboard was almost greyed out. It took about 15 minutes for it to recover to its normal brightness. Didn't affect the screen on my Bose Tonematch unit, though.