To cold crash you need to rack it, cool, and rack again. This will get the lees to fall to the bottom and you can rack off of them. There is a difference between cooling and cold crashing. I'm not sure about leaving it out at night. If it's below freezing, and you have a glass bottle it could freeze and crack. I'm not saying it will but it could. If I was going to cold crash I would want it to be in a more controlled enviroment.