Do the main computers have HDDs and not SSDs? If you came in and quickly warmed the house up, it could just be possible that condensation formed on the disks (or anywhere else inside the computer) since the air was warmed and the metal and other components would still be cold.
Even though the disks are enclosed, they still must have a small amount of air in them. The iPad is pretty much a sealed item with solid storage and so wouldn't get the problem.
Just a possibility.
This used to be a problem with installing video recorders in the winter. Take them into a warm house from a cold place and condensation would immediately form on the video head. They used to have a sensor for this but it was best not relied on. Better to wait a while.