I spent a week in warmer climes recently. While I was gone I left the heat completely off. I turned off the water and drained the pipes to prevent damage. I put all the houseplants in a small room in the basement with a tiny space heater.
I know that while I was gone, temperatures at a nearby airport were below 32F (0C) for some amount of time, but when I returned home, the temperature was back up to 40F, and had been for a day or so.
How can I tell whether the inside of the house reached sub-freezing temperatures?
Is there anything in my fully stocked pantry that might be a giveaway? Or in the toiletries cabinet?