My mistake on the temperature. I went back and looked here: http://www.weather.com/weather/tenday/CAXX0540 and the site gives it in degrees F, not C. Either way, it is cold. I went to the Spokane WA area forecast and saw highs this week in the low 40s F with rain and realized how warm that is by comparison.
I suspect there is information online about LF shooting in sub-freezing conditions. The bellows may be something to be careful of. You might need to leave the focus racked out to the lens focal length so the bellows only needs to flex slightly when you fine focus. It probably depends on the bellows material. Keeping the shutter as warm as possible so it doesn't slow down from the cold is probably the main thing. I don't know if there is any chance of light leaks when removing the darkslide from the light trap material not springing closed. You'll just have to experiment and have fun.