[Shin Pad]

If you don't have any plumbing or a vent or other penetration above the leak location area, and you have water coming in through the ceiling after a cold spell, one very likely cause would be gaps in your insulation. When the cold air hits the outside face of the vapour barrier, the moisture in the cold air will condense and freeze against the vapour barrier. This will build up over the cold spell, and then when it warms up, it will start to melt, thus causing water within your ceiling space. It will come through a lap joint in the vapour barrier or where there is a penetration through the vapour barrier such as a light fixture or similar.